Toro 724-Z Tractor User manual

Toro 724-Z Tractor User manual
ONAN T260G ENGINE SERVICE MANUAL
Table of Contents – Page 1 of 2
SAFETY PRECAUTIONS
GENERAL
PROTECT AGAINST MOVING PARTS
BATTERIES
FUEL SYSTEM
EXHAUST SYSTEM
EXHAUST GAS IS DEADLY!
COOLING SYSTEM
KEEP THE UNIT AND SURROUNDING AREA CLEAN
INTRODUCTION
EXHAUST GAS IS DEADLY!
GENERAL INFORMATION
INTRODUCTION
ENGINE MODEL REFERENCE
SPECIFICATIONS
DIMENSIONS AND CLEARANCES
ASSEMBLY TORQUES
ENGINE TROUBLESHOOTING
OIL SYSTEM
CRANKCASE OIL
OIL FILTER CHANGE
CRANKCASE BREATHER
PRESSURE LUBRICATION
FUEL SYSTEM
CARBURETOR
CARBURETOR OVERHAUL
PULSATING-DIAPHRAGM FUEL PUMP
AIR CLEANER
DASHPOT ADJUSTMENT
GOVERNOR ADJUSTMENT
IGNITION AND BATTERY CHARGING
BREAKER POINT IGNITION SYSTEM
IGNITION TIMING
ELECTRONIC IGNITION SYSTEM
IGNITION TIMING
BREAKER POINT AND ELECTRONIC IGNITION COILS
SPARK PLUGS
BATTERY INSPECTION
BATTERY JUMP STARTING
FLYWHEEL ALTERNATOR
ALTERNATOR OUTPUT TEST
STARTING SYSTEM
ELECTRIC STARTER
ONAN T260G ENGINE SERVICE MANUAL
Table of Contents – Page 2 of 2
ENGINE DISASSEMBLY
DISASSEMBLY/ASSEMBLY
VALVE SYSTEM
TAPPETS
VALVE FACE AND SEAT GRINDING
FLYWHEEL
GEAR COVER
GOVERNOR CUP
TIMING GEARS
PISTONS AND CONNECTING RODS
CYLINDER BLOCK
CRANKSHAFT
BEARINGS
CRANKSHAFT ENDPLAY
CHECKING CONNECTING ROD BEARING CLEARANCE
OIL SEALS
PISTON ASSEMBLY
INSTALLATION OF PISTON IN CYLINDER
CYLINDER HEADS
CYLINDER HEAD STUD TEST AND REPLACEMENT PROCEDURE
ALIGNING BLOWER WHEEL, VENTURI AND CHAFF SCREEN
Service
Manual
Engine
Safety Precautions
It is recommended that you read your engine manual and
become thoroughly acquainted with your equipment before
you start the engine.
This symbol if used warns of immediatehazardswhich
will resultin
severe personal injuryor death.
Thissymbolrefersto
ahazard or
WARNING unsafe
practice which can result in
severe personal injury or death.
Thissymbolrefersto
ahazard or
CAUTION unsafe
practice which can resultin
personal injury or product or property damage.
Fuels, electrical equipment, batteries, exhaust gases and
movingpartspresentpotentialhazards
that canresult in
serious, personal injury.Take care in followingthese recommended procedures. All local,state and federal codes should
be consulted and complied with.
Fuel System
DO NOT fill fuel tanks while engine is running.
DO NOT smoke or use an open flame in the vicinity of the
engine or fuel tank. Internal combustion enginefuels are
highly flammable.
Fuel lines must be of steel piping, adequately secured,
and free from leaks. Pipingat the engine should be
approvedflexible line.Donotusecopper
piping for
flexible lines as copper will work harden and become
brittle enough to break.
Be sure all fuel supplies have a positive shutoff valve.
Exhaust System
Exhaust products of any internal combustion engine are
toxic and can cause injury,
or death if inhaled. All engine
applications,especiallythosewithina
confined area,
should beequipped with an exhaust system to discharge
gases to the outside atmosphere.
Do not use exhaust gases to heat a compartment.
This engine is not designed or
inMake sure that your exhaust system is free of leaks.
tended for usein any type ofaircraft,
Ensure that exhaust manifolds are secure and are not
Use of this engine in aircraft can result in engine failure warped by bolts unevenly torqued.
and causes serious personal injuryor death.
k!!!!
Exhaust Gas is Deadly!
General
Provide appropriate fire extinguishers and install them in
convenient locations. Use an extinguisher rated ABC by
NFPA.
Make sure that allfasteners on the engine aresecure and
accurately torqued. Keep guards in position over fans,
driving belts, etc.
If it is necessary to make adjustments while the engine is
running, use extreme caution whenclose to hot exhausts,
moving parts, etc.
Exhaust gases contain carbon monoxide,apoisonous gas
that can cause unconsciousness and death. It is an odorless
and colorlessgas formed during combustionof hydrocarbon
fuels. Symptoms of carbon monoxide poisoning are:
Dizziness
Headache
Weakness and Sleepiness
Vomiting
Muscular Twitching
Throbbing in Temples
If you experienceany of these symptoms, get out intofresh air
immediately, shut down the unit and do not use until it has
been inspected.
Do not wear loose clothing inthe vicinity of moving parts,
such as PTO shafts, flywheels, blowers, couplings, fans,
belts, etc.
The best protection against carbon monoxide inhalation is
proper installation and regular, frequent inspections of the
complete exhaust system. If you notice a changein the sound
orappearance of exhaustsystem,shuttheunitdown
immediately and have it inspected and repaired atonce by a
competent mechanic.
Keep your hands away from moving parts.
Cooling System
Protect Against Moving Parts
Batteries
Before starting work on the engine, disconnect batteries
to prevent inadvertent startingof the engine.
Coolants under pressure
have a higherboiling point than
water. DO NOT openaradiatorpressure
cap when
coolant temperature is above 212F (100°C) or while
engine is running.
Keep the Unit and Surrounding Area Clean
DO NOT SMOKE while servicing batteries.Lead acid
batteries give off a highly explosive hydrogen gas which
can be ignited by flame, electrical arcing or by smoking.
Verify battery polarity before connecting battery cables.
Connect negative cable last.
Make sure thatoily rags are not
left on or near the engine.
Remove all unnecessary grease andoil from the unit.
Accumulated grease and oil can cause overheating and
subsequent engine damage and present a potential fire
hazard.
E-6
Table' ofContents
TITLE
PAGE
. l-1
.2-1
General Information
Speclflcations..
Dimensions and Clearances
Assembly Torques and Special Tools
Engine Troubleshooting
Oil System
Fuel System
Ignition and Battery Charging..
Starting System
Engine Disassembly
.3-1
.4-1
.5-1
.6-1
.7-1
.8-1
.9-1
.10-1
WARNING]
EXHAUST GAS IS DEADLY!
Exhaust gasesfrom all fuels (including diesel, gasoline, liquidpropane, natural
gas) contain carbon
monoxide, anodorless and colorless gas. Carbonmonoxide
is poisonous and can cause unconsciousness and
death. Symptoms ofcarbon
monoxide poisoningcaninclude:
Throbbing in Temples
Muscular Twitching
Vomiting
Inability to Think Coherently
Dizziness
Nausea
Headache
Weakness and Sleepiness
IF YOU OR ANYONE ELSE EXPERIENCE
ANY OF THESE SYMPTOMS, GET OUT
INTOTHEFRESHAIRIMMEDIATELY.
.If symptoms persist, seek medical
attention. Shut down the unit
and do not operate
until ithas beeninspected and
repaired.
Protection against carbon monoxide inhalation includes proper installation,
ventilation and regular, frequent visual and audible inspections
of the complete
exhaust system.
iii
General Information
INTRODUCTION
This manual deals with specific mechanical
and electrical information needed by engine mechanics for
troubleshooting, servicing, repairing,or overhauling
the engine.
Use only Genuine Onanreplacement parts to ensure
quality and the best possible repair and overhaul
results. When ordering parts, always use the complete Model and Spec number as well as the Serial
number shown on the nameplate.
Use the tableof contents for a quick
reference to the
separate engine system sections.
ENGINE MODELREFERENCE
Use the separate Parts Catalogs available at the
dealer level, for parts identification and for
establishing their proper location onassemblies.
Identify your model by referring to the
MODEL and
SPEC (specification)NO. as shown on the unit
nameplate Always use this number and the engine
serial number when making reference to your
engine.
The troubleshooting guide is provided
as a quick
reference for locating and correcting engine trouble. How to interpret MODEL and SPEC NO
The illustrations and procedures presented in each
section applyto the engines listedon thecover. The
flywheel-blower end of the engine is the front end
so
right and left sides are determined by viewing the
engine from the front.
2 6 0 G G A 024 1 A
1
The disassembly sectioncontainsmajoroverhaul
procedures for step by step removal, disassembly,
inspection,repairandassembly
of theengine
components.
2
3
4
5
6
7
98
1. Factory code for general identification of basic
engine series.
2. Number of cylinders.
3. Cubic inch displacement.
4. Engine duty cycle.
5. Fuel required (G=gasoline).
6. Cooling system description
(A=air-cooling-pressure).
7. BHP rating.
8. Factory code fordesignated optional equipment,
if any.
9. Specification (spec letter) which advances with
factory production modifications.
If amajor repair or an overhaul is necessary, a competent mechanic should either do the job orsupervise
and check thework of the mechanic assigned to do
the jobto ensure that all dimensions, clearances and
torque values are within the specifiedtolerances.
The wiring diagram on the last page of the manual
shows howtheelectricalcomponents
are interconnected.
A parts catalog (availableat the
dealer level) contains
detailed exploded views of each assembly and the
individual piece part numbers and their proper
names
for ordering replacement parts.
WARNING I
INCORRECT SERVICE OR REPLACEMENT OF PARTSCAN RESULT IN SEVERE
PERSONAL INJURY AND/OR EQUIPMENT DAMAGE. SERVICE PERSONNEL
MUST BE QUALIFIED TO PERFORM ELECTRICAL AND/OR MECHANICAL
SERVICE.
1-1
Specifications
This manual containsSI metric equivalents thatfollow immediately in parentheses
after the U.S. customary units of measure.
SPECIFICATION
Number of Cylinders
Bore
Displacement
Speed
(litre)
lockwise
ble
on
Compression
Rated
(Maximum)
Power at
Rated Speed
Oil Filter
Oil Capacity Without
Filter
Oil Capacity
Filter Change
Crankshaft Rotation
(viewed from flywheel)
Governor
Valve Clearance (Cold)
Intake
Exhaust
Spark Plug
A-E) (Spec
Breaker
Static
Point Gap
(Full Separation and
Cold)
Engine
Ignition Timing
Cylinder
T-260G
in
(
Stroke
SERIES
UNIT OF
MEASURE
m
m
RPM
BHP
( k w )
7.9)
in
(mm)
cu in
(cm3)
Qt
Qt
)
2
3.56
(90.48)
3.0
(76)
60
(983)
7.0 to 1
3600
24
(1
Full Flow
2.5
(2.4)
3.0
(2.8)
Speed Mechanical
in
(mm)
3)
in
(mm)
in
(mm)
in
(mm)
BTC
psi
(kPa)__
2-1
.005
(0.1
.013
(0.33)
.025
(0.64)
.020
(0.51)
20°
75 to 115
517 to 793
Dimensions and Clearances
All clearances given at room temperatureof 70°F (21 C) All dimensions in inches (approximate miilimetre dimensions in
parentheses) unless otherwise specified
DESCRIPTION
0.003
CYLINDER BLOCK
Cylinder Bore Honed Diameter
Maximum Allowable
Taper
Out-of-Round
Main Bearing Inside Diameter
(Without bearing)
Main Bearing Inside Diameter (Installed)
Camshaft Bearing Bore (Bearing Installed)
Interference Stud Height from Top Surface ofBlock
Spec C, D, E
Top2
Middle
(46.74)
(48.26)
1.84
1.904
(29.46)
(30.99)
1.16
1.22
Bottom
4
CRANKSHAFT
Main Bearing Journal Diameter
1.9992
(50.78)
Main Bearing Clearance
Spec A-E
Begin Spec F
Connecting Rod Journal Diameter
Crankshaft End Play
CONNECTING ROD
Large Bore Diameter (Without bearing installed
and rod bolts properly torqued
Connecting Rod Side Clearance
Piston Pin Bushing Bore (Without bearing)
Piston Pin Bushing Bore with Bearing,
(Finished bore)
Bearing to Crankshaft Clearance
Aluminum Rod
Iron Rod
CAMSHAFT
Bearing Journal Diameter
Bearing Clearance
End Play
Spec A-E
Begin Spec F
Camshaft Lift
Intake
Begin Spec A
Begin Spec E
SpecF
Begin
Exhaust
Begin Spec A
Begin Spec E
Begin
MINIMUM
Inches
(mm)
Inches
(mm)
3.5625
(90.49)
3.5635
(90.51)
2.1
87
(55.55)
2.0015
(50.84)
2.0040
(50.90)
1.3760
(34.95)
1.3770
(34.98)
(0.08)
0.003
(2.188
(55.58)
(52.32)
(50.80)
(2.06
2.00
2.0000
0.0025
(0.064)
0.0024
(0.061)
1.6252
(41.28)
0.005
0.0038
(0.097)
0.0042
(0.107)
1.6260
(41.30)
(0.13) (0.23)
0.009
1.7505
(44.46)
0.0020
(0.051)
0.8115
(20.61)
1.7510
(44.48)
0.0160
(0.406)
0.8125
(20.64)
0.7504
(19.06)
0.7508
(19.07)
0.0020
(0.051)
0.0033
(0.084)
0.0020
(0.051)
0.0033
(0.084)
1.3740
(34.90)
1.3745
(34.91)
0.0015 (0.038)
0.0030
(0.076)
0.0030
(0.076)
0.0120
(0.305)
(1.22)
0.048
(0.28)
0.011
(7.47)
0.294
(7.26)
0.286
(7.44)
0.293
(7.24)
0.285
(7.75) 0.305
(7.59)
0.299
(7.39)
0.291
(7.39)
0.291
(7.19)
0.283
SpecF
0.295
(50.80)
DESCRIPTION
MINIMUM
Inches
(mm)
MAXIMUM
Inches
(mm)
PISTON
Clearance in Cylinder
Measure 1.187Below Top of Piston and 90" from pin
.
. ..
Piston Pin Bore.. . . . . . . . . . . . ..
. .
. . , ... ... ..
Ring Groove Width
Top 1 Compression Ring . . . . . . .. . . .
. . . ..
No. 2 Compression Ring.. . . .
. . . . . . .. . . .. . .. . . ,
No. 3 Oil Control Ring . . . . . . . . . .
,
. . . . . . .. . . . ..
.
. .. . . ..
. . . . . .. .. . . . . . . . . .. . . .
. . . . . . . .. . . . . . . . . . . . . .. .
.. . .. ...
. . .. . . . . . .
. . . . . . . .. . . .. . . . . . .
PISTON PIN
Clearance in Piston .. . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . .. . . . . . . . .. . . .
Clearance in Connecting Rod
AluminumRod
Iron Rod . ... . . .. . . . . . . . . .. . . . .. . .. . . .. . . ... . .. . . . . . . . . .. . . .. ...
Diameter. . . . .. . . .. . . .. . .. .... . .. . ... . .. . .... . . . . . . . .. . ... . .. . ..
.
.
-PISTON RINGS
Clearance
Top Groove
Ring End Gapin Cylinder . .. . .. .. . ... . .... .. . . . .. . ... . .... .. . . ...
INTAKE VALVE
Stem Diameter .. . . . . . .. . . .. . .. .. . ... . .... . . . . ... .. . . . .... . . . . .. .
Clearance (Stemto Guide) . .. .. . . . . .. . ... . . .. . .. . . . .. . .. .. . .. . ...
Valve Face Angle . . ... .. .. . .. . .. ... .. . . . .. . ... .. .. . .. . . .. . . .. . .. .
tNTAKE VALVE SEAT
Seat Cylinder Head Bore Diameter..... . ... . .. . . . .. . . . . . .. .. . . . .. .
Seat Outside Diameter . .... ... . .... . .. . .... . . . . .... . .. . .. . . . . . . ..
Valve SeatWidth .. .... .. .. . .. ... . .. .. . .... . . . . .. .. . .. . .. .. . .. . ..
Valve SeatAngle .. . .. . . . ... .. . .. .. . .. . .. .. . .. . .. .. . .. . .. .. . .. . ..
EXHAUST VALVE
Stem Diameter .. .. ... . . . .. . .. . .. .. . .. . . .... ... . ... . . . . .... . .. . ..
Clearance (Stemto Guide) .. . ... .. . . . ... .. .. . .. . .. . . . .. . .. .. . .. . .
Valve Face Angle
EXHAUST VALVE SEAT
Seat Cylinder Head Bore Diameter... . . . . . .. .. .. . . ... . . . . . ... . .. . .
Seat Outside Diameter .. . .... . .. . .. .. . .. . .. . . . .. . .. . . . . . . .. . . .. . .
Valve Seat Width .. .. . .. . .... . .. . .... . .. . .. ... .. . ... . . . . . ... . ... .
Valve Seat Angle . .. . . . . . ... . .. . .. .. . .. . .. .. . .. . .. . . . .. . .. . . . .. .
VALVE GUIDE
InsideDiameter
TAPPET
Body Diameter . . . .. .. . . . . . . . . . .. . .. .. . .. . .. . . . . . . ... . . . . . . . . . .. .
Bore Diameter.. . . . . .. . . . . . . .. . .. . . .. . .. . . . . . . .. . .. . . . . . . . . . . . . .
Clearancein Bore
VALVE SPRINGS INTAKE AND EXHAUST
Valve Spring Free Length (Approx.). .. . . . . . . . .. . . . . . . .. . .. . . . . . . . .
Valve Spring Length
Valve Open.. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . .. . .. . . . .. . . . . . . .
Valve Closed
Spring [email protected] 1.375inch (Valve Closed).. . . . . . . . . . . . . . . . . . . . . . . . .
Spring [email protected] 1.125inch (Valve Open).. . .. . . . . . . . . . . . . . . . . . . . . . .
0.0090
0.0070 (0.1 78)
0.7502 (19.055) 0.7506
(0.229)
(19.065)
(2.032) 0.081
(2.032) 0.081
(4.775) 0.189
(2.057)
(2.057)
(4.801)
0.080
0.080
0.188
0.0001(0.003)
0.0005
(0.013)
0.0002
0.0002
0.7500
(0.005) 0.0008
(0.005) 0.0008
(1 9.05) 0.7502
(0.020)
(0.020)
(19.06)
0.002
0.010
(0.051) 0.008
(0.254) 0.020
(0.203)
(0.508)
0.3425
0.0010
(8.70)
0.3430
(0.025)
0.0025
440
(8.71)
(0.064)
1.5645
1.5690
0.031
(39.74) 1.5655
(39.85) 1.5700
(0.787) 0.047
45O
(39.76)
(39.88)
(1.194)
0.3410
0.0025
(8.661)
0.3420
(0.064) 0.040
440
(8.687)
(0.1 01)
1.2510
1.2550
0.031
(31.78) 1.2520 (31.80)
(31.88) .1.2560 (31.90)
(0.787) 0.047 (1.194)
45O
0.344
(8.74)
0.346
(8.79)
(18.99) 0.7480
(1 9.05) 0.7515
(0.038) 0.003
(1 9.00)
(1
9.09)
(0.076)
‘
.
3-2
0.7475
0.7500
0.0015
1.662 (42.21)
38 Ib.
71 Ib
1.125 (28.58)
1.375 (34.93)
42 Ib.
(17kg)
79 Ib
(32kg)
DESCRIPTION
MINIMUM
Inches
(mm)
GEAR BACKLASH
Timing Gear
Spec A-E
Begin Spec F
Oil Pump Gear
spec A-E
Begin Spec F
GOVERNOR
Dashpot to Governor Arm Bracket..
3- 3
MAXIMUM
Inches
(mm)
0.002
0.001
(0.051)
(0.025)
0.003
0.005
(0.076)
(0.127)
0.002
0.001
(0.051)
'(0.025)
0.005
0.008
(0.127)
(0.203)
0.040
(1.02)
0.060
(1.52)
Assembly Torques
The torque values given in Table 1 have been determined for the specific applications. Standard torque
valuesmust not be used where those listed in Table 1
apply. The engine assembly torques given here will
assure proper tightness without danger of stripping
threads. All threads must be clean and lubricated with
new engine oil before torquing.
Check all studs,nuts, and capscrews, and tighten as
required to keep them from working loose. Refer to the
PARTS MANUAL forthelocation
of washers and
capscrews.
TABLE 1.
TORQUE
SPECIFICATION
NmF1.-Lb.
8-10
1-14)
(1
7-9
(10-12)
TORQUE
DESCRIPTION SPECIFICATION
DESCRIPTION
NmF1.-Lb.
Cylinder Head Nuts (with
Compression Washers)
11-13
(15-18)
SpecA-E
14
Begin Spec F
(19)
Cylinder Head Nuts (without
Compression Washers)
(19-22)14-16
SpecA-E
17Spec (23)
Begin Spec F
Rear Bearing Plate
25-28
(34-38)
Begin
Spec
Connecting Rod Bolt
14-16
(19-22)
SpecA-E
Begin Spec F
(37-39)
27-29
Flywheel Capscrew.
(67-75)
50-55
Starting Mounting Bracket
(33-35)
24-26
to Oil Base Screws.
Gear Case Cover.
Oil Pump.
Intake Manifold Mounting
Screws
Valve Cover.
Exhaust Manifold Mounting
Screws
A-E
F
Other 14
/”/4" Cylinder Block Studs
and Nuts
Other 5/16" Cylinder Block
Studs and Nuts
Other 3/8” Cylinder Block
Nuts.
Special Tools
Thefollowingspecialtoolsareavailablefrom
Onan. For further informationsee TOOL CATALOG
900-0019.
Valve Seat Driver
Valve Guide Driver
Oil Guide and Driver
Combination Bearing Remover (Main andCam)
Combination Bearing Driver (Main andCam)
Flywheel Puller
4-1
4-8
(27-31)
( 5-11)
20-23
9-11
(27-31)
(12-15)
7-9
(10-72)
8-10
1-13)
(1
(24-31)
18-23
Engine Troubleshooting
I
IGNITION SYSTEM
FUEL SYSTEM
INTERNAL ENGINE
COOLING SYSTEM (AIR COOLED)
THROTTLE AND GOVERNOR
M-1686-1
5-1
Oil System
Oil level should be to the FULL mark ofthe dipstick. Start
engine and run for a short time to check for oil leaks
around the drain plug.
CRANKCASE OIL
Refer to engine nameplate or Periodic Maintenance
Schedule, located in theOperator'sManual,for
oil
change interval. If operating in extremely dusty, high
ambient, or low ambient conditions change oil more
often.
Run engine until thoroughly warm before draining oil.
Stop the engine, place a pan under the drain outlet and
remove the oil drain plug or open the drain valve. After
the oil is completely drained, replace the drain plug or
close the drain valve. Refill with oil of the correct API
classification and appropriate SAE viscosity grade for
the temperatureconditions.
Oil must meetor exceed the API designation SF, SF/CC
or SF/CD. Refer to the chart to determine the proper
viscosity grade of oil to use. Straight weight oils are
recommended for severeduty use and at temperatures
above 32" F (0°C) for minimumoil consumption.
WARNING
Crankcase pressure can blow out hot
Do NOT
oil andcauseseriousburns.
check oil while the engine is operating.
Hot crankcase oilcan cause burnsif
it is spilled or splashed on skin. Keep
fingers and hands clear when removing the oil drain
plug and wear protective clothing.
LS-1170
I
COOLING FINS
ALWAYS REPLACE
TIGHTLY OR OIL
LEAKAGE MAY OCCUR
FILTER
FILTER 2. OIL FILTER
OIL FILTER CHANGE
Refer to engine nameplate or Periodic Maintenance
Schedule, located in the Operator's Manual, for oil filter
change interval. If operating in extremely dusty, high
ambient, or low ambient conditions change oil more
often.
Spin off oil filter element and discard it. Thoroughly
clean filter mounting surface and makesure new gasket
is inserted in the element.
FIGURE 1. CRANKCASE OIL FILL
Do not overfill crankcase. Excess
oil
CAUTION causes
higheroperatingtemperatures and may cause foaming.
6-1
Apply a thinfilm of oil to the gasket. Spin element down
by hand until gasket just touches mounting pad and
then turn down an additional 1/2-3/4 turn. Do not
overtighten.
Clean orreplace crankcase breather baffle periodically.
Be sure baffle material-doesn’tcome apart and work into
manifold.
the
To disassemble, remove breather hose from cap and
valve assembly. Remove cap and valve assembly and
wash in asuitable solvent. Replacecap and valve if balls
do not move freely.Pull baffle out and wash in solvent.
To allow free operation of the valve, screens must be
positioned as shown in Figure 3.
With oil in crankcase, start engine and check for leaks
aroundfilter element. Retighten only as much as
necessary to eliminate leaks;do not overtighten.
PRESSURE LUBRICATION
CRANKCASE BREATHER
All engines usean oil pump to provide a constant flow
The crankcase breather prevents pressure from
of oil to the engine parts. The oil supply collects in the
buildingupin
the crankcase. It also prevents oil
oil base where it is picked up by the oil pump pick-up
contaminationby removing moistureor gasoline
cup. A by-pass valve is used tocontroloil pressure.
vapors and other harmful blow-bymaterials from the
Drainoil beforeremoving oil base and always use a
crankcase. Thesevapors are routed to thecarburetor
new gasket when replacing the oil base.
where they are mixed with incoming air and burned in
the combustionchamber. A sticky breather valve can
cause leaks, highoilconsumption,rough
idle,
reduced engine power andarapidformation
of
sludge and varnish within the engine.
Oil Pump
The oil pump (Figure 4) is mounted behind the gear
cover and isdriven by the crankshaft gear. Inlet pipe and
screen assembly are attached directly to the pump
Crankcase Breather Service
body. A discharge passage in pump cover registers with
Thisengine uses. a crankcase breather valve for
a drilled passage in the crankcase. Parallel passages
maintaining crankcase vacuum. Ifthe crankcase
distribute oil to the front main bearing, rear main
becomes pressurized as evidenced by oilleaks at the
bearing, and pressure control bypass valve.
seals, clean baffle and valve in a suitable solvent.
OIL PUMP PICK-UP CUP
BREATHER
HOSE
CAP AND V A L V E
HOSE CLAMP
OIL PUMP ASSEMBLY
CRANKCASETURNED
ON LEFT SIDE
LS-1109
FIGURE 3. CRANKCASEBREATHER
FIGURE 4. OIL PUMP ASSEMBLY
6-2
Circumferential grooves in the main bearings supply The valve is non-adjustable and normally does not
oil to connecting rod bearings through drilled pasneed maintenance. Determine if valve is operating
-.,sages from eachmainjournal.
A drilled passage
normally by inspecting plunger action
as follows:
\connects thefront mainbearing oil supply t o the front
'camshaft bearing; rear cam bearing
is splash lubrica1 . Remove the 3/8 x 24 x 7/8 cap screw located
ted. Oil overflowfromthebypass
valve provides
behind gear cover and under governor
arm.
lubrication to thecamshaft drivegears.
2. Remove spring and plunger with amagnet tool.
Normal oil pressure should be 30 psi (207 kPa) or
3. Determine proper valve operation by checking
higherwhen the engine
is at normal operatingtemperature. If pressure drops below this
the spring and plunger according to the following
value at governed
measurements.
speed, inspect oil system for faulty components.
Plunger Diameter..
Check oil pump thoroughly for worn
parts. Oil pump
to prime it before reinstalling.
Except for gaskets and
pick-up cup, component parts of the pump are not
available individually. Install new
a pump assembly if
any parts are worn.
0.3105 to 0.3125 in.
(7.89 to 7.94 mm)
Spring
Free Length..
1.00 inch (25.4 mm)
Load
2.6Ifr0.2 Ibs. (11.6+0.9N)
when compressed to 0.5 inch (12.7 mm)
4. Check the valve seatand cleanaway anyaccumulation of metal particles which could causeerratic
valve action. Verify that the valve
is not
seat
damaged.
Oil By-Pass Valve
The by-pass valve (locatedto theright and. behind
gear
cover, Figure 5) controlsoilpressurebyallowing
excess oil to flow directly backtothe
crankcase.
Normallythevalvebeginstoopenabout
20 psi
(138 kPa).
5. Clean plungerand springin parts cleaningsolvent
and install.
FIGURE 5. BY-PASSVALVE
6-3
Fuel System
CARBURETOR
Set the adjustment screw about 1/8 turn outward
(rich) from the midpoint of this range. On Nikki
carburetors the idle adjustment is limited to 1/8
turn.Do not go beyondtheselimits.
The carburetor mixture screw settings weresetfor
maximum efficiency at the factory and should normally
not be disturbed. If adjustmentsseem necessary, first be
suretheignition
system isworkingproperlyand
governor sensitivity is properly adjusted.
If adjustment is needed, refer to Figures 1 and 2 and
proceed as follows:
THROTTLE
Forcingthemixtureadjustment
CAUTION screw
tight will damage the needle
and seat. Turn in only until light tensioncan be felt.
1. Walbro mixture screw settings:
FS-1406-2
Turn both mixture screws in until lightly seated
(Figure l), then back the idle mixture screw out 1/2
turn and
the
main
mixture screw out 1-3/4 turns.
NlKKl CARBURETOR WITH SEMI-AUTOMATIC CHOKE
AND LIMITED IDLE MIXTURE SCREW.
N i k k i limited idleadjustmentmixturescrew
settings:
The carburetor has a limited idle adjustment range
between stops
1/8 turn. The screw should only
be adjusted within these limits; in to lean the
mixture, out to richen. There is no main mixture
adjustment.
MAIN FUEL
ADJUSTMENT
When replacing the idle mixture screw, turn in until
lightly seated, then back screw out 1-1/2turns.
Replace limiter cap so the
tab
is approximately
centered.
IDLEFUEL
ADJUSTMENT
FS-1002
WALBRO CARBURETOR
2. Start the engine and allow it to warm up thoroughly
(at least 10 minutes).
FIGURE 1. CARBURETOR
ADJUSTMENT
Some equipment manufacturersmay require higher
throttle stop speed and governor low speed rpm
settings. Referto equipment manufacturer’s Operator’s Manual for thecorrect rpm settings. When rpm
settings are not specified by the equipment manufacturer use therpm settings listed in Steps 3 and
5.
5. Readjust the throttle screw for 1000 rpm idle, then
adjust the governor low speed screw for 1100 rpm
idle.
6. Move the engine speed control to the fast position.
Bend the high speed stop on the governor so the
engine runs at the vehicle manufacturer’s recommended speed (Figure 2.)
3. Move the engine speed control to the slow position.
Back out the low speed screw on the governor so
the throttle stop screw on the carburetor controls
engine speed (Figure 2). Adjust the throttle stop
screw for 1000 rpm idle.
7. Check the main mixture adjustment (Walbro carburetors only) by rapidly accelerating the engine
from idle to full speed. Theengine should accelerate
evenly and without hesitation. If it does not, turn the
main adjustment screw out in 1/8 turn increments
until the engine accelerates smoothly, but do not
turn it out more than 1/2turn beyond the original
setting.
4. Determine the best idle mixture setting by first
turning the idle adjustment screw in until engine
speed drops and then outward until engine speed
drops again. Over a narrow range between these
two settings, engine speed remains at its highest.
7-1
In general, overhauling a carburetor consists of disassembly, a thorough cleaning, and replacement of
worn parts. Carburetorrepair parts are available.
THROTTLE STOP
SCREW
General instructions for overhauling a carburetor
are
given below. Carefully note the position of all parts
while removing to assure correct placement when
reassembling Read through all the instructions
before
beginningforabetterunderstanding
of theprocedures involved. Carburetor componentsare shown
in Figure 3.
HIGH SPEED
Ignition of fuel can cause serious
WARNING personal
injury or death by fire or
explosion. Do not permit any flame, cigarette, or other
igniter near the fuel system.
I
GOVERNOR ARM
FS-1119
FLOAT ASSEMBLY
FRONT PULL GOVERNOR
THROTTLE STOP
SCREW
IDLE ADJUSTMENT
THROTTLE PLATE
GOVERNOR CONTROL\
NIKKI CARBURETOR
GOVERNOR SPRING
GOVERNOR
CHOKE PLATE
STOP ADJUSTMENT
SIDE PULL GOVERNOR
FIGURE 2.
GOVERNORSPEEDADJUSTMENT
CARBURETOROVERHAUL
Carburetionproblemsthat
are notcorrectedby
mixture adjustmentsare usually aresult of gummedup fuel passages or worn internal parts. The most
effective solution is a carburetor overhaul.
WALBRO CARBURETOR
FIGURE 3. CARBURETOR
ASSEMBLY
FS-1440-3
RemovalRepair
and
1. Remove air cleaner and hose.
2. Disconnect governor and throttle linkage, choke
control and fuel line from carburetor.
3. Remove the four intake manifold cap screws and
lift
complete manifold assembly from engine.
4. Remove carburetor from intake manifold.
Cleaning
1. Soak all metal components not replaced in carburetor cleaner. Do not soak non-metal floats or
other non-metal parts. Follow the cleaningmanufacturer’s recommendations.
2. Clean all carbon from the carburetor bore, especially
where the throttle and chokeplates seat. Be
careful
not to plug the idle or main fuel ports.
Disassembly (Walbro)
1. Remove throttle and choke plate retaining screws,
then plates. Pull out throttle and choke shafts.
2. Remove main jet and idle adjustment needle.
3. Remove attaching screws andseparate upper and
lower carburetor sections.
4. Carefully note position of float assemblyparts,then
pull out retaining pin andfloat assembly.
5. Remove needle and unscrew needle valve seat.
3. Dry out allpassages with low pressureair (35PSI).
Avoid using wireor otherobjectsfor cleaning which
may increase the size of critical passages.
4. Check thecondition oftheadjustmentneedle;
replace if damaged. Replacefloat if loaded withfuel
or damaged.
5. Check the choke andthrottle shafts for excessive
play in their bore. This condition may necessitate
replacement of the carburetor.
Disassembly (Nikki limited idle adjustment)
1. Remove main jet and idle adjustment needle.
2. Remove attaching screws andseparate upper and
lower carburetorsections.
3. Carefully note position of float assembly parts,then
pull out retaining pin andfloat assembly.
4. Remove needle valve.
BEND FLOAT
TANG HERE
TO ADJUST
6. Replace old components with new parts.
0.02 0.02 INCH
(0.51 0.51 mm)
I
FUEL LEVEL
0.25 INCH
(6.35 mm)
BEND FLOAT ARM
HERE TO ADJUST
MINIMUM
FLOAT DROP
0.20 INCH
(5.08 mm)
NO FUEL
WITH FUEL
FLOAT LEVEL ADJUSTMENT
FS-1524
WALBROCARBURETOR
MINIMUM
FLOAT DROP
FUEL LEVEL
.472
2913"
(12.0 mm)
.0512"
.028"
WITH FUEL
FLOAT LEVEL ADJUSTMENT
BEND FLOAT ARM
HERE TO ADJUST
NlKKl CARBURETOR
FIGURE 4. CARBURETORFLOATLEVELADJUSTMENTS
7-3
NO FUEL
FS-1683
Reassembly and Installation (Walbro)
1. Install needlevalveand seat, main jet and fioat
assembly. Makesure that float pivot pin is properly
placed and that float moves freely
without binding.
2. Gently push float tang down until needle just seats.
(Figure 4). Measure float level; adjust if necessary.
Release float tang and measure float drop; adjust if
necessary.When checking float level anddrop,
measure to float body, not seam.
3. Position gasket oncarburetor and attach carburetor
sections together with screws.
4. Slide in throttle shaft and install plate using new
screws. Before tightening the screws, the
plate must
be centered in the bore. To do so, back off the
throttle stop screw as necessary and completely
close the throttle lever. Seat the plate by tapping
with a small screwdriver, then tighten screws. Install
the choke shaft and plate in the same manner.
5. Install idle adjustment screw, throttle stop screw,
and main fuel adjustment needle.
6. Mount carburetor on intake manifold and install
assembly on engine.
7. Mount air cleaner assembly. Connect air intake
hose,breatherhose, fuel line,vacuumline, and
throttle linkage.
8. Adjust carburetor and governor according to directions given in this section.
Reassembly and Installation
(Nikki limited idle adjustment)
1. Install needle valve, main jet, and float assembly.
Make sure float pivot pin is properly placed and f l o a /
moves freelywithout binding.
2. Turn carburetor on its side and measure float level
(Figure 4). Adjust float level only if necessary.
Measure float drop (the distance from the top of
carburetor body to top offloat). Adjust only if
necessary.
3. Position gasket on lower carburetor section and
install upper carburetor section.
4. Install idle adjustment screw, throttle stop screw,
and fixed main jet plug.
5. Mount'
carburetor on intake manifold and install
assembly on engine.
6. Mount' air cleaner assembly. Connect air intake
hose,breatherhose, fuel line, vacuum line, and
throttle linkage.
7. Adjust carburetor and governor according to directions given in this section.
VALVE
PUMP BASE
DIAPHRAGM
\
ASSEMBLY
SCREWS
REED VALVE
FIGURE 5. EXPLODED VIEW OF FACET FUEL PUMP
PULSATING-DIAPHRAGM FUELPUMP
Pulsating-diaphragm fuel pumps, or pulse pumps, rely
on changes in crankcase vacuum to create a pulsating
movement of thepumpdiaphragm. As the engine's
pistons move outward, a vacuum is created. This
vacuum is transmitted to the pump diaphragm, causing
it to pull back and suck fuel into the pump. As the
engine's pistons move inward, crankcase vacuum is
reduced and the diaphragm return spring pushes the
pump diaphragm forward, forcing fuel through the
pump outlet.
Fuel Pump Test Procedure
Before testing make certain that fuel pump vacuum line
connections are tight and free of leaks.
1. Operate engine at anidle for five minutes to ensure
that carburetor is full of fuel.
2. Shut engine off and remove fuel inlet line from fuel
pump.
WARNING
WARNI
NG
Spilled fuel can ignite and cause
serious personal injury or death.
Thoroughly clean-up any spilled fuel.
?
?
3. Connect a vacuum gaugefuel
topump inlet using a
piece of fuel hosewith clamps.
4. Start engine and allow to idle. foratleast
seconds. Record vacuum gauge reading.
five
5. Move throttle control to high idle position. Wait at
leastfivesecondsandrecordvacuumgauge
reading.
Fuel Pump Repair
This section applies only
to Facet fuel pump. TheNikki
fuel pump is notrepairable; replace unit if test readings
are notwithin the values specified in TABLE 1.
1. Remove the vacuum and fuel lines. Inspect the
lines forwear, cracking or brittleness. Replace
as
necessary.
2. To' insure correct alignment
when reassembling,
scribe a line across the outer pump parts on each
end of the pump.
3. Holding the pump carefully, remove the assembly
screws (Figure 5).
4. Carefully pullapart thepump sections and check
for worn or damaged parts. Replace with new
parts where necessary or install pumprepair kit.
5. Check and unclog if necessary the small diaphragm air bleedholelocatedbehindthepump
diaphragm in the pumpbase.
6. Shut engine off and remove vacuum gauge hose
from fuel pump inlet. Connect fuel inlet line to fuel
pump.
i
!
7. Remove
fuel
outlet line from
fuel
pump.
Spilled fuel can ignite and cause
WARNING
serious personal injury ordeath.
Thoroughly clean-up any spilled fuel.
8. Connect a pressure gauge
to fuel pump outlet using
a pieceof fuel hose with clamps.
diaphragm air bleed
CAUTION Ahoeloleclogged
can cause diaphragm wear
and seal damage while inhibiting pump operation.
9. Start engineandallow
to idle foratleastfive
seconds. While holding pressure gauge level with
pump outlet, record pressuregauge reading.
6. Replace gaskets and reassemble pump. Reinstall
assembly screws, checking the scribe marks
for
proper alignment.Reinstall fuel and vacuum
lines
and clamps.
10. Move throttle control to high idle position and allow
engine to run for at least five seconds.
While holding
pressure gauge level with pump outlet, record
pressure gauge reading.
WARNING
Usecare when reassembling
and reinstalling the pump. Improper parts alignment or misconnectedfuel lines
can result in leaking fuel, creating a serious fire
hazard.
11. Shut engine off and remove pressure gauge hose
from fuel pump outlet. Connect fuel outlet line to fuel
pump.
Repair or replace the
fuel pump if test readings are not
within the values specified in TABLE 1.
AIR CLEANER
If air cleaner becomestoodirty,
engine will not receive sufficient air
to run' properly.Symptoms: Loss of power, flooding,
hard starting and overheating.
TABLE 1
PULSE PUMP TEST SPECIFICATIONS
Pump *outlet
Pressure
(Minimum)
Low Idle
High Idle
2.6 inches
of mercury
2.6 inches
of mercury
Engineisequipped
with apaperelement.
If the
engine is equipped with polyurethane
precleaner, it
must be removed, cleaned and oiled every25 ofhours
operation, or more under extremely dusty conditions.
1. To clean precleaner,wash in water and detergent
(Figure 6). Remove excess water by squeezinglike
a sponge and allow
to dry thoroughly.Distributetwo
tablespoonsof SAE30 engine oilevenly around the
precleaner. Knead into and wring excess oil from
precleaner.
1.7 psi
1.7 psi
7-5
1. WASH
2. SQUEEZE DRY
3. COAT WITH OIL
4. INSTALL OVER PAPER
ELEMENT
POLYURETHANE
PRE-CLEANER
SAFETY
COVER
FS-1131
FIGURE 7. AIR CLEANERASSEMBLY
2. Depending on conditions in which the engine is
operating, theinnerpaper
element shouldbe
replaced whenever it becomes excessively dirty or
oily.
2. Holding throttle against throttle stop screw, adjust
dashpot to obtain 0.050 inch (1.27 mm) clearance
(Figure 8).
3. Secure dashpot to air cleaner support bracket with
CAUTION
Never run engine withair cleaner
removed. Dirt will enter engine
and wear out rings causing excessive blow-by.
hex nut.
CAUTION
.-
DASHPOT ADJUSTMENT
Do not grip dashpot with a pliers;
I internal
damage
may occur. If
necessary hold dashpotby hand when tightening
hex nut.
On engines equipped with a dashpot, adjust as follows:
1. Pull governor arm and linkage (awayfrom carburetor) until throttle stop contacts throttle stop
screw.
DASHPOT
ARM BRACKET
THROTTLE
TOP SCREW
STOP
FIGURE 8. DASHPOTCLEARANCE
7-6
GOVERNOR ADJUSTMENT
THROTTLE STOP
SCREW
These engines are adapted for use wherea wide range
of speedsettings is desired. Engine speed is controlled
atany given point betweenminimumandmaximumby
simply shifting the throttle lever on the dash panel until
the desired speed is reached.
CARBURETOR
THROTTLE PLATE
A reliable
instrument
for
checking
engine
speed is
required for accurate governor adjustment. Engine
speed can be checked with a tachometer.
t
HIGH SPEED
Check thegovernor arm, linkage,throttle shaft, and
lever forabindingconditionor
excessive slack and
wearat connectingpoints. A bindingcondition at any
point willcause the governor to act slowly andregulation will be poor. Excessive looseness may cause a
hunting
condition
and regulation
could
be erratic.
Work the arm back and forth several times by hand
whiletheengineisstopped
to checkfor above
conditions.
FRONT PULL GOVERNOR
If the governor is hunting or not operating properly,
adjust as follows (Figure 9).
1. Disconnect linkage (A) fromone of holes (C).
2. Push linkage (A) and governorarm(B) as far back
THROTTLE
SCREW
(toward carburetor) as they will go.
3. Holding linkage andgovernor arm toward direction of carburetor,insertend
of linkageinto
whichever hole (C) in governor arm lines up the
closest. If between two holes, insert in next hole
out. Install clip tosecure rod toarm.
THROTTLE PLATE
GOVERNOR CONTROL
LINKAGE
On side pull governor the governor spring is set by the
factory in the third hole of thegovernor arm. (Third~hole
from pivot). On
front pull governors the governor spring
is set by the factory in the second hole of the governor
armadapter.(Second hole from pivot.) To increase
sensitivity, move spring loop into a hole closer to the
pivot. To decrease sensitivity, move spring loop into a
hole farther away from the pivot. After sensitivity has
been
recheck the low speed rpm setting. Adjust if
necessary.
GOVERNOR SPRING
GOVERNOR
set
PIVOT
GOVERNOR
SHAFT YOKE
SIDE PULL GOVERNOR
FIGURE 9. VARIABLESPEEDGOVERNORADJUSTMENTS
7.7
Ignition and Battery Charging
!
BREAKER POINT IGNITION SYSTEM
This section applies to those engines equippedwith an
automotivetypebattery
ignition system.Bothspark
plugsfire simultaneously, thus the need for distributor
a
is eliminated. To maintain maximum engine efficiency,
change the breaker points every 200hours of operation.
7. Replace breaker box cover, coil wire, spark plugs,
and spark plug cables.
Continuity Test
As a check for proper ignition timing
a continuity test
may be performed:
1. Adjust breaker points
IGNITION TIMING
The timing is preset atthe factory. Slight timing changes
can be made by adjustingthe point gap.
2. Remove blower housingto expose timing marks on
top of gearcase coverand flywheel (Figure 2).
Breaker Point Replacement and Adjustment
1. Remove spark plugs.
2. Removebreaker boxcover. Rotate crankshaft
clockwise (facing flywheel) until points are fully
open.
FLYWHEEL TIMING
(TC) MARK
3. Remove condenser (screw
A) and detach condenser
lead and coillead (screw B) See Figure 1.
4 . Remove two Allen screws (C) and lift breaker
assembly from engine.
5. Replace condenser and pointassembly with new
partsandreinstallusing
reverse order of removal.
M-1397
above procedure in
6. Adjust point gap by rotating crankshaft clockwise
(facing flywheel) by hand until the points arefully
open. Set the point gap (using flat feeler gauge) at
0.020 inch (0.51 mm) by adjusting the socket head
screw (D) inward or outward
(Figure 1). A0.020 inch
point gap is equivalent to 20" BTC. Make sure feeler
gauge is clean and free of any grease,oil or dirt.
FIGURE 2. TIMING MARKS
3. Rotate flywheel clockwiseuntil timing mark is
alignedwiththe
proper timing mark (Figure 2)
located on topof gearcase cover. Refer to SPECIFICATlONS for proper number of timing degrees.
4. Connect an ohmmeter or acontinuity test lamp set
across the ignition breaker points. Touch one test
prod tothe coil lead terminal (screw B, Figure 1).
5. Touch the other
test prod to a good ground on the
engine.
6. Turn crankshaft against rotation (counterclockwise) until the points
close. Then slowly turn the
crankshaft with rotation (clockwise).
FIGURE 1. SETTINGPOINTGAP
7. The lamp should go out or continuity lost just
as
the pointsbreak which is where ignition occurs. If
timing is early (advanced) the point gap is too
large. If timing is late (retarded) the pointgap is
too small. Adjust point gap accordingly.
WARNING
Failuretogroundsparktester
away from spark plug hole may
result in ignitionof cylinder gases andmay cause,
severe personal injury.
ELECTRONIC IGNITION SYSTEM
This section applies to those engines equipped with an
electronic battery ignition system. Both spark plugs fire
simultaneously, thus the need for a distributor is eliminated. The electronic ignition module is located on the
engine gear cover behind the flywheel. The module
receivesa timing signal from the magnets
located within
a trigger ring which rotates on the engine crankshaft
(Figure 3). If the electronic ignition is suspected of malfunctioning, proceed as follows:
2. Pull spark plug wires off spark plugs and remove
spark plugs. Connect an approved spark tester to
each of the sparkplug wires and ground them away
from spark plug hole. Turn key onand crank engine
over for 5 seconds while watching for spark. If a
spark occurs regularly, the problem is not in the
ignition system. If no spark occurs, go to step 3.
Never putjumper lead tothe coil
CAUTION
negative terminal. Thiswillcause
failure of the electronic ignition module.
3. Connect a jumper lead directly from the positive
battery terminal to the positive
coil terminal
(smaller diameter of the two threaded posts). Crank
engine over while watching forspark. If spark
occurs, the problem is in the low oil pressure cut out
switch or relatedwiring, the lubricating system (low
oil. pressure), or in the other circuitry bringing
voltage to the coil. If no spark occurs, go to step 4.
4. Refer to IGNITION COIL section to test coil for
proper resistance. If coil checks out good, go to
step 5.
I
IGNITION
MODULE
ES-1670
5. Connect positive side of voltmeter to negative
coil terminal (larger diameter of the two threaded
posts) and negative side ofvoltmeter to engine
ground. Turn key on and rotate flywheel slowly by
hand while observing voltmeter.Voltage should
switch back and forth between battery voltage and
1-1.5. If voltage does not switch properly, replace
ignition module.
FIGURE 3. IGNITION MODULEANDTRIGGERRING
1. Check all electrical connections to be sure they are
clean and tight. If all connections are good and
wiring is intact, go to step 2.
electronicignitionwill
WARNING dThe
e
viledeliver
r
WARNING
full voltage
to
the
spark
plugs even when rotatedby hand. Care should be
6. Install spark plugs and wires. If ignition module is
being replaced, be sure to connect red lead from
new ignition module to positive (+)terminal of coil,
black lead from module to negative
terminal of
coil.
taken to avoidan electrical shock.
WARNING
Failure to remove spark plugs
beo
fe
rbefore turning engine over may
result in engine starting, whichmay cause severe
personal injury.
CAUTION
of
failure
8-2
Neverput B+ lead tothe coil
negative terminal. This willcause
the electronic ignition module.
T h e ignition timing is preset at the factory and is not
adjustable. Fortroubleshooting purposes, it is possible
to make an approximate check of the ignition timing by
removing blowerhousingandusingthe
gearcase
timing marks.
4. Rotate the flywheelslowly by hand
in the clockwise
direction until the voltmeter reading jumpsfrom
approximately 1 volt to battery voltage. Atthis point
the flywheel timing mark should line up with the
proper timing degree
(see SPEClFlCATlONS) mark
located on the gearcase timing marks. To recheck
timing, the flywheel must be rotated another complete revolution in the clockwise direction. Moving
the flywheel back and
forth across the timing
marks
will not activate theelectronic ignition control.
5. Install spark plugs, wires, andblower housing.
BREAKER POINT AND ELECTRONIC,
IGNITION COILS
Totestprimary and secondary windings within the
ignition coil first make sure theignition power isoff and
coil is at room temperatureof 70°F (21 "C).
FLYWHEEL TIMING
(TC)MARK
1. Use, a Simpson 260 VOM or equivalent.
2. Place a black leadon the negative coil terminal
andared leadonthe positive
coil terminal.
Primary resistance should read between 3.87-4.73
o h m sfor breaker point coils, and between 2.90-3.60
for electronic ignition coils.
M-1397
FIGURE 4.
IGNITIONTIMING MARKS
3. Change resistance settingonohmmeter.Place
ohmmeter leads inside on spark plug cable holes
(Figure 5). Secondaryresistanceshouldread
between 12,600-15,400 ohms for breaker point
ignition coils, and between 14,500-19,800ohms for
electronic ignition coils.
4. If any of the above conditions are not met, replace
coil.
Continuity Test
1. Pull spark plug wires off spark plugs and remove
spark plugs and blower housing.
OHMMETER
toremovesparkplugs
CAUTION bfailure
eo
fe
rbefore turning
engine
over
may
result in engine starting, whichmay cause severe
personal injury.
2. Turn ignition on.
3. Connect a voltmeter between the negative
coil
terminal (larger diameter the
of two threaded
posts)
and a good engine
ground.
WARNING
Theelectronicignitionwill
deliver full voltage
spark
the
to
plugs even when rotatedby hand. Care should be
taken to avoid anelectrical shock from the spark
plugs.
FIGURE 5. COILTEST
SPARK PLUGS
BATTERY JUMP STARTING
Checkandregap
spark plugs every 100 hours of
operation (Figure 6). Replace spark plugs that show
signsof fouling or electrodeerosion.
Occasionally,it may be necessary to jump start(charge)
a weak batteryusing a charged boosterbattery. If jump
starting is necessary, the following procedurerecom
is
mended in order to prevent starter damage, battery
damage and personal injuries.
Do not engage starterforperiods
CAUTION
CAUTION
Ionger than 30 seconds without
allowing 5 minutes for starter to cool. Starter failure
may result if these guidelines are not followed.
1 . Disconnect engine load.
2. Use only a battery of the same voltage (12V) as is
used with your engine.
3. Attach one end
of the positive booster cable(red)to
the positive
terminal of the boosterbattery.
Attach the other end of the positive cable to the
positive terminal of your engine battery.
FIGURE 6. SPARKPLUGGAP
BATTERY INSPECTION
4. attach one end of the negative (-) booster cable
(black) to negative (-) terminal of booster battery.
Attach otherend of negative cable to a solid chassis
ground onyour engine.
Check battery cells with a hydrometer. (Figure 7). The
specific gravity reading should be
approximately 1.260
at 77OF (25°C).
If one or more
cells are lowon water,add distilled water
and recharge. Keep the battery case
clean anddry. An
accumulation ofmoisture will lead to amore rapid
discharge and battery failure.
Do not allow the positive and
WARNING
negative cable ends to touch
each other because it will short the battery causing
Keep the battery terminals clean and tight. Push the
cable terminal down
flush with or slightly below thetop
of the battery post(Figure 8).After making connections,
coat the terminals with a light application of petroleum
jelly or greaseto retard corrosion.
Poor contact at the battery cable connectionsis often a
source of trouble. Make sure battery
cables are in good
condition and that contacting surfaces are clean and
tightly connected. Do not reverse battery leads. Use
recommended batterytools when disconnecting leads
to avoid mechanical batterydamage.
hazardousarcing,which
personal injury.
can causesevere
5. Jump starting in any other manner may result in
damage to the battery or theelectrical system.
6. Turn ignition switch to ON to start engine.
Never jump start
a frozen battery.
WARNING
too do so can cause the battery to
explode. Never exposethe battery to an open flame
or an electrical spark because a battery generates
highly explosive hydrogen gas.
Ignition of explosive battery gases
can cause severe personal injury. Do
not smoke while servicing batteries.
SPECIFIC
GRAVITY READING
SHOULD BE
1.260 at 77'F (25°C)
BATTERY POST
CABLETERMINAL
FIGURE 7. SPECIFICGRAVITYTEST
FIGURE 8. BATTERYCABLECONNECTION
8-4
FLYWHEEL ALTERNATOR
This unit is equippedwith a permanent magnetflywheel
a l t e r n a t o r and solid-state voltage regulator-rectifier
,output control). See Figure 9. As with all solid-state
electrical units, precautions are necessary when servicing. Observe the following:
This engine uses a 12 volt, negative
CAUTION- ground
CAUTION
system.Alternatormustbe
connected to battery atall timeswhenengineis
running. Do not reverse battery cables.
2. The regulator-rectifier has built in protectionagainst
open circuits or short circuits on the
alternator
output (B+) terminal. Eithercondition willcause the
regulator-rectifier to shut offand appear as if it is not
functioning Prior tochecking the regulator-rectifier,
check all wiring between the regulator-rectifier B+
terminaland thebattery positive
terminalto
assure it is free of open
circuits, resistances orshort
circuits. Also, if the batteryis extremely discharged
it mayhave insufficient power to “turn on”the
regulator-rectifier.
Weak ignition spark or a discharged battery indicates
trouble in the charging system. But before testing the
engine’s chargingsystem, alwayscheck the battery for
serviceability.
3. Be sureregulator-rectifierplug(connector)is
Keep thesepoints inmind when testing or
servicing the
flywheel alternator:
4. Make sure alternator stator leads are not shorted
together.
inserted properly. Plug must bottom in receptacle;
thiseliminates any resistancedueto
a poor
connection. Keep clean andtight.
5. Be sure regulator-rectifier has agoodground
connection. Mating surface for mounting must be
enough to recharge battery after each start. Charging
clean andfasteners tightened properly.
system tests require
a full charged battery. Alternator
output is reduced in direct proportion to engine
rpm.
Also, power required for accessories reduces power 6. Never reversethe battery leads.
available to recharge battery.
1. Be sure engine is being run long enough and
fast
MOUNTED ON
CYLINDER COVER
B+
STARTER
IGNITION)
FLYWHEEL
MOUNTED BEHIND
BLOWER WHEEL
--
VOLTAGE REGULATOR
ES-1333
TO BATTERY
CAUTION:
REGULATOR MUST BE GROUNDED
THROUGH MOUNTING BOLTS
VOLTAGE REGULATOR
CONNECTIONS
.___-_-
FIGURE 9. FLYWHEELALTERNATORSYSTEM
ES-1332
With the engine running between 1800 to 2600 rpm,
observe the panel ammeter (if not already equipped,
connect atestammeter). If no charging is evident,
proceed with the AlternatorOutput Test.
and from battery negative terminal to regulatorrectifier case. If battery voltage remains low with
engine running, proceed tostep 3.
3. Disconnect plug from regulator-rectifier and test
the AC voltage atthe plugwith engine running near
3600 rpm. If AC voltage reads more or less than
specified in Table 1, proceed tostep 4. If AC voltage
is as specifiedbut DC voltageislow,replace
regulator-rectifier.
ALTERNATOR TEST
OUTPUT
Use a volt-ohmmeter such as the Simpson 270, when
testing the charging system.
1. With the engine running, check battery
the
terminal
voltage(regulatoroutput) using a DCvoltmeter.
Voltage output should
be within the valuesspecified
in Table 1. If voltage is greaterthan specified
replace regulator-rectifier assembly. If voltage is
less than specified,proceed to step 2.
2. Examine all wires for loose, corroded,broken
connections, short
circuits, etc. Check fuses. Repair
as neededto assurecompletecircuitsfrom regulatorrectifier B+ terminal to battery positive terminal
4. Use the R x l scale on the ohmmeterfor detecting
opens in the stator (unit not running Disconnect
plug fromregulator'-rectifier.Connectohmmeter
test leads to wires coming fromstator.Refer to
Table 1 for resistancespecifications. If resistance is
not as specified,replace stator. If stator resistance
readings areas specified and windings arenot
shorted to ground, low AC voltage may be due to
loss of magnetism If so, blower wheel assembly
must be replaced Check for magnetism with steel
tool blade. Next,connect one ohmmeter testlead to
stator wire,connect the other testlead to ground. If
the ohmmeter reading is low the
stator is grounded
and must be replaced.
TABLE 1. TESTING 15- AND 20-AMPERE SYSTEMS
PROCEDURE-.
I
1. Battery
Battery
Voltage
unit not
running.
2. Regulator Battery Voltage after
3 to 5 minutes.
12 VDC
12 VDC
13.6 to 14.7 VDC
13.6 to 14.7 VDC
0.1 to 0.2 Ohms
0.3 to 0.5Ohms
40 VAC minimum
60 VAC maximum
31 VAC minimum
51 VAC maximum
unit is running
3. Alternator Stator
and Wiring
Ohmmeter reading from stator
output
unit not running.
Check at plug.
4. Alternator
and Wiring
Measure AC open circuit stator voltage
with unit running. Measure between
two stator leads with plug disconnected
and unit running at approximately 3600 rpm.
8-7
ENGINE WIRING DIAGRAM
(Solenoid Shift Type Starter)
8-8
Starting System
ELECTRIC STARTER
2. Disconnect battery cable and electrical lead wires
from starter.
Normally the starterwill require little or no service other
than possible brush replacement.However, if through
accident ormisuse, the starter requires service or
overhaul, the following information will provide the
information necessary to perform this service.
3. Remove blower housing and cylinder airhousing.
4. Remove flywheel andstartermotor.
Starter Disassembly (Inertia Type)
Service
Remove through-bolts and separateend
housing, and armature (Figure 1).
When starting engine, note starter motor action. The
pinion gear should mesh quickly with flywheel ring gear
and spin engine. Once engine starts and solenoid
opens, the startershould disengage and stop. If starter
cranks engine slow, or not at all, check start circuit
components. Failure to crank is normally caused by low
battery charge, defective battery cables, corroded or
poor connections, or low temperatures. If after checking
these variables,startercontinues to crank slowly, starter
must be removed and repaired.
cap,
2. Disassemble drive assembly and drive end cap by
loosening the self-locking stop nut.
3. Inspect starter for damagedor worn parts.
4. Repair or replace all damaged or worn parts, as
needed.
Starter Assembly (Inertia Type)
Starter Removal
1. Before reassembling the starter, wipe off any dirt
WARNING Accidental
starting
ofinjury
the engine can
WARNING
causesevere
personal
of
death.Disconnectthebatterycableswhenrepairs
are
from parts with a clean cloth or blow off with filtered,
compressedair.
made to the engine, controls, or housings.
CAUTION
engine
clean
inped
1. Remove both battery cables from battery. Discon-
nect ground cable first.
Donotimmersebearings
in
cleaning fluid. Use a brush dipremoval.
oil
dirtfor
SEAL
I
THROUGH BOLT
\
ARMATURE
I
STOP
NUT
END CAP
\
PINION GEAR
BRUSHES
\
-__-
BRUSH SCREWS
INPUT STUD
NUT
FIGURE 1. STARTER
MOTOR
(INERTIA
TYPE)
9-1
ES-1334
StarterDisassembty (Solenoid Shift Type)
2. Assemble brushes so thatthechamferedside
is
away from the brush springs. Make sure brush
wires do not rub against commutaor
the
or endcap.
1. Remove “M”terminalnutandwireleadfrom
solenoid (Figure 2).
3. Torque brush screws
to a valueof 3 to 3.5 ft-lbs (4 to
5 Nm).
nut stud
4. input
Torque
7 Nm).
of valueto a
2.Remove the two solenoid mounting screws and
remove solenoid.
4 to 5 ft-lbs (5 to
5. Apply a thin film of grease to the commutator end of3.
the armature shaft and to the portion of the shaft that
contacts thebearings.Applyagenerous
film of
silicone base grease (GE Versilube 322-L) to the
threads.
shaft
6. Torque stop nutto a value of 20 to 25 ft-lbs (27 to
34 Nm).
Scribe a mark across frame and rear bracket to aid
in assembly.Remove the two through bolts.
4.rear
Remove
and
bracketassembly.
frame
armature
5.remove
Carefully
from
and lever
front
bracket. Notedirection of lever and retainer.
7. Torque throughbolts to a valueOf 4.5 to 6 ft-lbs (6 to
8 Nm).
8. Apply a small amount of a silicone based grease
(GEVersilube 322-L)to armature shaft spline.
9. Install dust cap, pinion gear, dustcover spacer,
anti-drift spring, stop nutwasher, and stop nut.
6. Remove the
two
brush
mounting
screws,
and
remove the rear bracket.
7. Remove brush holderassembly from theframe by
pulling the brushes
out.
10. Push dust cover on until it snaps into position.
SOLENOID
THROUGH
THRUST
FRONT
BRACKET
BUSHING
BRUSH
BRUSH
HOLDER
ASSEMBLY
FIGURE 2. STARTERMOTOR (SOLENOID SHIFT TYPE)
8. Push stopper toward pinion andremove snap ring
(Figure 3).
Removestopperandoverrunningclutchfrom
armature shaft.
\
STOPPER
SNAP RING
ES-1194
FIGURE 4. INSTALLING
STOPPER
Es-1622
4. Lubrication: When starter motoris assembled apply
grease to each of the following points (Recommended grade: Multemp PS No. 2):
FIGURE 3. REMOVINGOVERRUNNINGCLUTCH
Armature shaft spline
Both bushings (Both ends of armature)
Stopper on armature shaft
Pinion gear
'Sliding portion of lever
10. Inspect starter for damaged or worn parts.
1. Repair or replace all damaged or worn parts, as
needed.
5. Fit overrunning clutch into lever, and install with
armature in the front bracket.
Starter Assembly (Solenoid Shift Type)
1. Install seal in nosehousing. Install overrunning
clutch on the armature shaft.
6. Install leverretainer and spacer. Position frame
assembly over armature on the front bracket.
7. Install brush holder assembly. Position brushes in
brush holder. Make certain positive lead wires are
not grounded.
2. Slide stopper on the armature shaft. Position snap
ring in groove in armature shaft.
8. Install washers,asrequired,ontherearendof
armature shaft to obtain an armature shaft thrust
gap of 0.05 to 0.5 mm (0.002 to 0.02 inch). New
washers are required if rear bracket is replaced.
3. Pull stopper all the way over snapring (Figure4). It
may be necessary to tap snap ring into groove with a
punch while maintaining tension on stopper.
Table 1. Starter Assembly Torques
9. Install rear bracket. Secure brush holder
to rear
bracket with two machine screws.
9-3
10. Install and tighten the two throughcapscrews.
11. Install soienoid plungerin lever. Securesolenoid to
front bracket with two machine screws.
12. Install wire lead to the terminal “M”on solenoid.
13. Afterassembly,adjust
pinion clearance. Pinion
clearance should be 0.020 to 0.080 inch (0.5 to
2.0 mm); if not, check as follows. See Figure 5.
A. Connectstarter to a battery, as shown in
Figure 5. Close switch. This willshift pinion into
cranking position.
B. Push pinion backby hand andmeasure pinion
clearance. If clearance does not fall within the
specified limits, adjust by adding or removing
shimslocatedbetweensolenoidandfront
bracket.Addingshimsdecreasesclearance;
removingshims increases clearance. Shims are
included with replacement solenoid.
ES-1001
FIGURE 6. TESTINGARMATUREFORGROUNDS
Inspecting tor an OpenCircuit in Armature: Using an
ohmmeter, check for continuity between the commutator
segments. If there is no continuity (high resistance), the
segments are openand armature must be replaced.
Testing Armature tor a Short Circuit: Use agrowler for
locatingshorts in the armature. Place armature in
growler and hold
a thin steel blade (e.g. hacksaw blade)
parallel to the core and
just above it while slowly
rotating
armature in growler(Figure 7). A shorted armature wi
cause the blade
to vibrate and beattracted to the core. It
armature is shorted, replace witha new one.
PINION
STOP RING
FRONT BRACKET
J
HACK S A W
FIGURE 5. PINION CLEARANCEADJUSTMENT
Inspection and Testing
Inspect thestarter components formechanical defects
before testing for grounds orshorts.
TestingArmature tor Grounds: Touch armature shaft or
core and the end
of each commutator barwith a pair of
ohmmeter leads (Figure 6). A low ohmmeter reading
indicates a grounded armature.Replace grounded
armature.
9-4
ES-1002
FIGURE 7. TESTINGARMATUREFORSHORTCIRCUITS
Commutator Inspection: If commutator is dirty or
discolored, clean with number 00 to 000 commutator
paper. Blow grit out of armature aftercleaning.
Check for shorts between positive side of brush holder
and brush holder base. If there is continuity, replace
holder assembly. Check for free movement of brushes.
All brushes should move freelyin the brush holders.
commutator is scored, rough, or worn,
turn it down in a
lathe.
Overrunning Clutch: Inspect pinion and spline teeth for
wear or damage.
Inertia type starter inspection
If pinion gear is worn or damaged,inspect flywheel ring
gear also. Rotate pinion. It should turn free when turned
in one direction, and lock when turned in the opposite
direction.
Housing Inspection: Permanent magnetsare glued to
inside of the housing. Magnets mustsecure
be and free
of cracks.
Do not clean overrunning clutch in in
solvent or liquid cleaning solution.
Washing theclutch will cause the grease to leak out.
BrushInspection: If brushes are worn shorterthan
1 / 4 inch (6.35 mm), replace them. Check to see that
brushes movesmoothly in the brush holders. See
Figure 8.
Solenoid: Push solenoid plunger in and release it. The
plunger should return to its original position. While
holding plunger all thewayin,
check for continuity
between terminals “M” and
“B”. Ifthere is no continuity,
replacethe solenoid (Figure
10).After replacing solenoid
check pinion clearance.
0.25 inch
FIGURE 8. BRUSH WEAR LIMIT
TERMINAL “B”
Pinion Gear: If pinion gear is badly worn, has broken
teeth,or pinion splined sleeve is damaged replace
pinion gear and dust cover assembly. If pinion gear is in
good condition, wipe armature shaft spline and pinion
clean.
Solenoid shift type starter inspection
Field Coil: Use an ohmmeter to check for continuity
between brushes. If there is nocontinuity, the field coil is
open and must be replaced. With field coil mounted in
the frame,check for continuity between the field coil and
frame. Replace frame assembly
if there is continuity.
ES-1345
FIGURE 10. SOLENOID
TERMINALS
Brushes: Cleanaround brushes and holders, wiping off
all brush dust and dirt. If brushes are worn shorter than
11.5 mm (.4528 inch) replace them (Figure 9).
Bushings: If either the front or rearbushing show signs
of wear or damage,
replace them. Bushing and rear
bracket are replaced as an assembly. Check armature
shaft thrust gap if rear bracket is replaced.
Remove front bushing by tapping bushing from inside
with a 7/16 inch tap. Do not remove cap from front
bracket. Thread capscrew, same size astap, into
bushing. Using a slide hammer remove bushing from
front bracket, Press new bushing into front bracket. Use
care not to distort inside diameter of bushing.
11.5mm
(.4528 inch)
/-
+
WEAR
LIMIT
ES-1193
FIGURE 9. BRUSHWEAR LIMIT
9-5
Brush Replacement:Cut old positive brush from pigtail
at the brush. Be careful not to damage field coil. Clean
1 / 4 to 3/8 inch (6.5 to 9.5 mm) of brush end of pigtail
with sandpaper or emerycloth (Figure 11).
FLYWHEEL RING GEAR
0.020 0.015 inch (0.51 0.38 mm)
STARTER GEAR FREE TRAVEL WHEN
ENGAGED WITH FLYWHEEL GEAR
PIGTAIL
STILL ATTACHED
TO
FIELD
COIL
SMALL CHAMFER
(approx. CLEAN
1/4 to 3/8inch)
MUST NOT
EXTEND BEYOND
BRUSH SURFACE
LARGE CHAMFER
STARTER MOTOR
PINION GEAR
REPLACEMENT
BRUSH
ES-1003
FIGURE 11. BRUSH
REPLACEMENT
FIGURE 12. CHECKING STARTER GEAR LASH
Push prepared end of pigtail lead into hole in replacement brush from the small
chamfered side. Solder
pigtail
lead to replacement brush on the large chamfered side,
using 50/50tin/lead, rosin core solder and a standard
240/325 Watt soldering iron. Use a file to remove any
excess solder thatmay extend beyond brush surface.
CAUTION
Pigtail lead must not protrude from
surface on the soldered side
of brush.
Toprevent stiffening of pigtaillead to not use excessive
amount of solder andheat.
Starter Mounting
Before installing starter motor, make sure the starter
mounting surfaceon the enginebase is clean and
free
of oil.
5. To adjust lash on starterswithout slotted mounting
holes, remove starter. Use
a 21/64 inch(8.334 mm)
drill to enlarge one mounting
hole in starter mounting
bracket.
6. Install starter motor and adjust lash to 0.020 in.
0.015 in: (0.51 mm 0.38 mm).
starter mounting
7. Remove flywheelandtorque
capscrews to 24 to 26 ft-lbs (33 to 35 Nm). Use Onan
flangehead capscrews orSAE grade 8 capscrews
with ahardened flatwasher.Do not use lockwashers.
Failure totorquestarterbolts
CAUTION
properly may cause starterfailure
and ring gear damage.
8. Install flywheel spark plugs, blower housing, and
cylinder air housings.For correct cylinder air
housing installation (required on somemodels),
refer to Cylinder Air Housing Clearance.
To install starter on T-260G (Spec A) engines use the
following procedure. On these engines starter pinion
gear lash requires adjustment and must be checked
when starter is installed.
Install startermotor and
tighten mounting capscrews
just enough to hold starter in place.
to
Connect
9. Connect battery cable and wiresstarter.
battery cables to battery. Connectground cablelast.
To install starter onT-260G (BeginningSpec B) engines
use the following procedure.On these engines starter
pinion gear lash does not require adjustment.
Remove spark plugs from the engine. This allows
free movement of the flywheel.
1. Install starter motor
and torque mounting capscrews
to 24 to 26 ft-lbs (33 to 35 Nm).
Manually pull the starter pinion gear outward on its
shaft until pinion gear teeth mesh completely with
flywheel ring gearteeth.Energize
solenoid on
solenoid shift starter.
2. Install flywheel, blower housing, and cylinder air
housing. For correct cylinder air housing installations (required on some models), refer
to Cylinder
Air Housing Clearance.
Measure the amount of free travel (lash) between
the pinion gear teeth and the ring gear teeth. See
Figure 12. If lash is too tight, causing binding and
slow starter operation,
or if lash is greater than0.035
inch (0.889 mm), lash must be adjusted.
to starter.Connect
3. Connect battery cable and wires
battery cables to battery. Connectground cablelast.
9-6
another
EngineDisassembly
DlSASSEMBLY/ASSEMBLY
1. Use the
proper
bearing
driver to install front main
bearing after coating it with a light film of oil.
2. Insertrearmain bearing in rear bearing plate.
3. Insert crankshaft, rear bearing plate, and crankshaft
When complete enginedisassembly is necessary, first
remove all completeassemblies. Individual assemblies
such as fuel pump and carburetor can bedisassembled
at
and repaired
4. Install piston and connectingrods.
5. Install camshaft and gearassembly; align crank
gear mark with cam gear mark.
6. Install valveassemblies, oil pump, oil base,and
cylinder heads.
Suggested Disassembly Order
1. Drain crankcase.
2. Disconnect all exhaust lines and electrical lines.
3. Remove engine from its mountings and place on a
suitable bench or work stand.
4. Remove all housings, shrouds, blower housings,
etc.
5. Remove flywheel, using a puller. Note position of
chaff screen and venturi when removing to assure
screw holealignment on reassembly. See page
1018 for further information.
6. Remove ignition trigger ring, if engine is equipped
with electronic ignition.
7. Remove the gear cover,being careful to protect the
oil seal from keyway damage.
8. Remove the crank gear, using a gear puller and ring.
9. Remove all accessories such as oil filter, starter,
intake manifold, fuel lines, spark plugs, etc.
10. Remove breaker point box.
11. Remove oil base, oil pump and cylinder heads.
12. Remove valves, springs, lifters, etc.
13. Remove camshaft and gear assembly.
14. Remove connecting
rods
pistons.
and
15. Removerearbearingplate,crankshaft,
and front
bearing.
Keep all parts in their respective orders. Keep valve
assemblies together. Return
rod caps
to their respective
pistons. Analyze the reasons for parts failure.
7. Install breaker point box.
8. Install all accessories suchas oil filter, starter, fuel
lines and spark plugs.
9. Install gear cover
with oil seal, triggerring (electronic
ignition only) and flywheel.
10. Set breakerpoints (if equipped withpoints) to obtain
proper timing.
11. Check valve clearance.
12. Install all housings andair cleaner.
13. Fill' crankcase withoil.
Operation
Start engine and check oil pressure. Run for approximately 15 minutesto bring engine
to operating temperature. Check for oil leaks, fuel leaksand exhaust leaks.
Adjust carburetor and governor for speed
and sensitivity.
Testing Compression
Thecompression tester isusedto
determinethe
condition
valves, of
pistons, piston rings and cylinders.
To check compression:
1. Run the engine until thoroughly warm.
2. Stop engine and remove spark plugs.
3. Remove air cleaner and placethrottle and choke in
the wideopen position.
4. Insert the compression gauge in one spark plug
hole.
5. Crank the engine andnote the reading.
Refer to SPEClFlCATlONS section for compression
pressures. There maybe variations due to equipment,
temperature, atmosphericconditionsand altitude. These
pressures are for a warm engine at cranking speed
(about 300 rpm).
Suggested Assembly Procedure
Engine assembly is normally the reverse of the disassembly procedure observing proper clearancesand
torques. usea torque wrench to assureproper tightness.
Coat the internal engine parts with oil astheyare
assembled.After the internal engine parts are assembled, theengine shouldturn over byhand freely. Use
onlygenuineOnanpartsandspecialtoolswhen
reassembling your engine.
10-1
VALVE SYSTEM
Tappet Adjustment
Theengine isequipped with
adjustable valve tappets.
The valve tappet clearance should be checked and
adjusted, if necessary, at least every 200 operating
hours or when poor engine performance is noticed.
Adjust the valve clearance only when engine is at
ambient temperature. Proceed as follows:
1. Remove ignition key to prevent accidental starting.
2. Remove all parts necessary to gain access to
valve tappets.
3. Remove spark plugs to ease the task of turning
the engine over by hand.
A properly functioning valve system is essential' for
good engine performance. All engines utilize an Lhead type valve design as shown in Figure 1. Access
to the valve system can be obtained by removing
cylinder heads and the valve covers on top of the
engine. A valve spring compressor must be used to
remove valves from the cylinder block.
A valve stem sealis sometimes used on the intake valve
guides of some engines. This seal must be replaced
each time the valve is removed.
4. Place a socket wrench on the flywheel
capscrew
and rotate the crankshaft
in a clockwise direction
until the left intake valve (viewed from flywheel
end) opens and closes. Continueturningthe
crankshaft until the TC mark on the flywheel is
lined up with the mark
TC on thegear cover. This
should place the left piston (#1)at the top of its
compression stroke. Verify that the left intake and
exhaust valves are closed and there is nopressure
on the valve lifters.
valve adjustment
5. The correct feeler gauge for the
(see SPEClFlCATIONS) should pass freely between valve stemandtappet;a
0.002 inch
(0.05 mm) thicker gauge should not (Figure 1).
Place valves, springs,retainers,and tappets in a rack as
they are removed from cylinder block so they can be
identified and reinstalled in their original locations.
Discard old valve stem seals and replace with new ones
during assembly.
i
Usethe following procedures to inspect and service the
valve system.
Inspection
Clean carbonfromthe
valves,valveseats,valve
guides, and cylinder block.
Valves: Check the valve face for evidence of burning,
warpage, out-of-round, and carbon deposits.
6. To correct the valve clearance, use a 7/16-inch
open end wrench to turn the adjusting screw to
obtain the correct clearance. The screw is selflocking and willstay where it is set. A 9/16-inch
(14 mm) open end wrench is required
to hold the
tappet while turning the adjustingscrew.
Burning and pitting
are caused by thevalve failing to
seat tightly. This condition is often caused by hard
carbon particles on the seat. It may also be due to
weak valve springs, insufficient tappet clearance;
warpage, and misalignment.
7. To adjust valves on the righthand cylinder, turn
engine one complete revolution and again
line up
mark on theflywheel and the
TC mark on thegear
cover. Then follow adjustment procedure given
for left hand cylinder.
8. Replace all parts removed in Step 2. Tighten all
screws securely. Torque manifold boltsto specified torque.
VALVE CLEARANCE
V A L V E ADJUSTINGADIUSTING
V A L V E RETAINER
VALVE SEAT
V A L V E SPRING-
)
\\I
V A L V E SPRING
VALVE ROTA.TOR
FIGURE 1. VALVE
ASSEMBLY
10-2
YT-1005
Warpage occurs chiefly in theupper stem due to its
exposure to intense heat. Out-of-round wear follows
when the seat is pounded by a valve whose head is
not in line withthe stem and guide. If a valve face is
b u r n e d or warped, or if the
stem is worn, install new
a
'valve.
Driving out old guides can damage
CAUTION
the guide or tappet bores. Be careful
not to strike guide bores with driver or allow guide to
strike tappet bores during removal.
Valve Guide Installation: Run a small polishing rod
covered with crocus cloth through
valve guide holes
to clean out carbonand other foreignmaterials. Place
a new gasket on the intake
valve guide, and coat the
outer edge of each new guide with oil.Place guide,
notch-up, in cylinder block and press in until guide
stops or protrudes 11/32 inch (8.7 mm) from rocker
box side of block. A suggested method of installation
is shown in Figure 3.
Too much clearance in the intake guide admits air
and oilintothecombustion
chamber, upsetting
carburetion, increasingoil consumption, and making
heavy carbon deposits. Carbon reduces heat dissipation. Clean metal is a good heat conductor but
carboninsulatesandretains
heat. This increases
combustion chamber temperatures which causes
warping and burning.
Unburnedcarbonresiduegums
valve stems and
causes them to stick in the guide. Deposits of hard
carbon with sharp points projecting become white
hot and cause pre-ignition and pinging.
ROD
Refinish valves that are slightly pitted or burnedanon
accurate valve grinder. If valves are badly pitted or
have a thin margin when refacing, replace them.
NUT
5/16-18 HEX, NUT
(2 REQUIRED)
\
VT-1020
FIGURE 2. VALVESTEMANDVALVEGUIDEINSPECTION
(2 REQUIRED)
StemsAnd Guides: Always check valve stems and
guides for wear(Figure 2). Use a hole gauge to measure
the valve guide. When
clearance with stem exceeds that
specific in DlMENSlONS AND CLEARANCES, replace
either valve or guide or both, as may be necessary.
Always regrind seat to make concentric with the newly
installed guide.
2-3/8”
(60 mm)
5/8" (16 (mm)
Vl-1023
Worn valve stem guides can be replaced from inside
the valve chamber (a seal is providedbehindthe
intake valve guides only). The smaller diameter of the
tapered valve guides must face toward thevalve head.
chamber
Tappets are alsoreplaceable from the valve
after first removing the valve assemblies.
FIGURE 3. VALVEGUIDEINSTALLATION
Valve Stem Seals: Do notreuse valvestem seals. Each
time the valves are removed from cylinder block, a
new seal must be used when valve is reinstalled.
Valve Guide Removal: Before removingvalve guides,
usean electricdrillwith
awirebrush
to remove
carbonandotherforeignmaterialfromtopsurface
of
guides. Failure to perform this operationmay result in
damage to the guidebores. Drive the guides
out with
a hammer and valve guide driver.
CAUTION installed
not remove valve after seal is
CAUTION
Valve canbe withdrawn
only as far as the groove in valve stem. Do not allow
valve stem seal
to come contact
in
with groove or seal
damage will result.
10-3
Valve Seat Removal: Remove carbon and combustion
deposits from valveseat. Select proper puller size
determined by inside diameter of valve seat. On some
pullers use a new seat asa guide to adjust puller depth
(Figure 4). Puller jaws must expand into cylinder block
at the point where bottom of valve seat insert rests
cylinder block. Position puller on valve seatand tighten
hex nut. Clampcylinder block to a solid bench. Attach
slide hammer to puller. Tighten hex nut between each
blow with the slide hammer.
Valve Spring: Check valve springs for cracks, worn
ends, distortion, and tension. If spring
ends are worn,
check valve spring retainer for wear. Check for spring
distortion by placing springa on
flat surface next
to a
square. Measure height of spring and rotate
it against
squareedge to measure distortion. If distortion
exceeds 0.06 inch (1.5 mm) replace spring. Check
spring tension at the installed height for
both the
valve open and closed position using an accurate
valve spring tester. Replace any valve spring that is
weak, cracked, worn, or distorted.
Valve Rotators: Positive type valve rotators prolong
valve life and decrease valve repairs. When functioning properly, the valve is rotated a fraction of a
turn each time it opens. While at open position, the
valve must rotate freely. There is
no easy way to
determine if a valve rotator is good or bad. Onan
recommends that valve rotators be replaced at each
major overhaul orif a build-up of carbon is noted on
valve face and valve seat.
VALVE SEAT
Valve Seats: Inspect valve seat inserts. If seats are
loose, cracked or severely pitted, new ones must be
installed. Remove valve seatinserts using avalve seat
removal tool. If valve seat insert bores in cylinder
block are damaged or wornso that apress fit cannot
be obtained when installing new standard size valve
seat inserts, theboresmustbemachined
for an
oversize seat.
(USE PROPER TOOL
VALVE SEAT
CHECK THIS SURFACE
FOR BURRS BEFORE
USE NEW VALVE SEAT TO
ADJUST PULLER DEPTH
i
VT-1025
FIGURE 5. INSERTINGNEWVALVESEAT
Valve Seat Installation: After the old seat has been
removed, clean out any carbon or metal burrs from the
seat insert recess. Use a valve seat insert driver and
hammer to install the insert (Figure 5). Drive the valve
seat insert in so that theinsert enters the recess evenly.
Make certain that the valve seat insert rests solidly on
the bottom of the recess all the way around its
circumference.
To assure a tight valve seatfit and eliminate the danger
of seat loosening in the bore, valve seat must
be staked.
PULLER JAWS
Insert valveseatstaker into valveseator guide in
cylinder block. Using a lead hammer, strike the staking
tool asharp blow towedge new valve securely in place.
It will be necessary to refinish valve seatinserts before
installing valves.
C-1104
FIGURE 4. VALVE SEAT REMOVAL
10-4
TAPPETS
Refinish valve faces to a 44" angle on a valve refacing
machine.
The first cut fromvalve face must be a light
Very little wear takes place on tappet diameters or in
grinding.
Check if there is an unevenness of metal
tappet bores. If the clearance between tappet and
being
removed.
If only part of valve's face has been
in cylinder blockexceeds specifications, replace
touched,
check
to
see if valve is properly seated in
he tappet.
machine or if valve is warped, worn, or distorted.
When cut is even around the whole valve face, keep
Inspectthe tappet faces whichcontactcamshaft
grinding until complete
face is-groundclean. Be sure
lobesfor roughness, scuffing,or concave wear.
the correct valve face angle is maintained. When
Replace any worn tappets. If tappets are worn,
valve head is warped, a knife edge will be ground
inspect camshaft for wear.
(Figure,7) on part or allof the head due to the large
amount of metal that must be removed to completely
VALVE FACE AND SEAT GRINDING
reface valve.Heavyvalveheads
are requiredfor
Some engines are equipped with a premium valve
strength and good heat dissipation. Knifeedges lead
package (aluminized intake valves). If thealuminized to breakage, burning, and pre-ignition due to heat
valve face does not clean-up using awire brush, the
localizing on theedge.
valve face may be refinished.This removes the
aluminized coating from thevalve
face. An aluminized
Replace any valve that cannot be entirely refaced
valve that has been refinished will normally have a life
while keeping a good valve margin (Figure 7) or is
expectancy equalto a standardvalve. If longer valve
warped, worn, or damaged in any way. The amount of
life is required, worn or damaged valves should be
grinding' necessary to true a valve indicates whether
replaced with new premium valves.
valve head is worn or warped.
Before installing new valves or previously used valves,
inspect valve seats for proper valve seating. If used
valves are reinstalled,the valve stems should be
cleaned and valve faces ground to their specified
angles of 44". Refinish valve seats to a 45" angle.
When refacing valves and seats, remove all evidence
of pitting and grooving. If end ofvalve stem is pitted
or worn, true it and
clean it up on refacer
the
wheel. A
very light grind is
usually enoughto square stem and
remove any pits or burrs.The valve guide should be
'thoroughly cleaned. If valve guide is worn, or valve is
warped, the necessary parts must be replaced.
WARPED
VALVE WITH
KNIFE EDGE
KNIFE EDGE
GOOD MARGIN
By grinding thevalve
face and seat at slightly different
angles, a fine line of contact on face and seat is
obtained,eliminatingthe need to lapthe seating
surfaces. The one degree difference in angles is
defined as theinterferenceangle
(Figure 6). The
seat angle is greater than that of the valve face. This
assures contact at the maximum diameter on valve
seat seating surface.
1/16 INCH
(1.6 rnm) MINIMUM
M-1184
FIGURE 7. VALVEHEADMARGIN
When new valve seats are installed, or previously
used seats reground, refinishingmust be done with a
valve seat grinder used according to the manufacturer's directions.
Valve seatsshould be ground with a45 degree stone
and the width
of the seat band shouldbe 1/32 inch to
3/64 inch (0.79 to 1.2 mm) wide. Grind only enough
to assure proper seating.
VT-1021
FIGURE 6. VALVEINTERFERENCEANGLE
10-5
Place each valve in its proper location. Check each
valve for a tight seat. Make several marks at regular
intervals across the valve face using machinist's
bluing.' Observe if the marks rub off uniformlywhen
the valve is rotated partof a turn against the seat. The
valve seat should contact thevalve face evenly at all
points. Theline of contact should be
at the center of
the valve face.
FLYWHEEL
GEAR COVER
Removing theflywheel is a relatively simple process,
but the following
procedure must be followedto avoid
damage to the gear case and possible injury to the
operator.
After removing the mounting screws, tap the gear cover
gently with a soft faced hammer to loosen it.
When installing the gear cover, make
sure that the pin in
the gear cover engages the nylon lined (smooth) hole in
the governor cup (Figure 9). Turn the governor cup so
that the nylon lined hole is
at the three o’clock position.
Use a small amount of grease to assist in holding
governor cup in position. Thesmooth side ofthe
governor yoke mustride against the governor cup. Turn
the governor arm and shaft clockwise as far as
possible
and hold in this position until the gear cover is installed
flush against the crankcase. Be careful not to damage
the gear cover oil seal.
1. Turn theflywheel mounting screw outward about
two turns.
Do not remove the screw comWARNING
pletely since it acts as arestrainer when the flywheel snaps loose. If the
flywheel is not held by the screw, the spring
action in the
wheel will cause it to fly off
with great
force which can cause lnjury to the operator.
2. Install a puller bar on the flywheel (Figure 8).
FLYWHEEL
3/4
GOVERNOR ARM
MOUNTING SCREW
GOVERNOR SHAFT A F T
ROTATE
GOVERNOR CUP
SO T H A T R O L L P I N
F I T S INTO T H E
METAL LINED
HOLE OR PLASTIC
BUSHING I N T H E CUP
cs-loo0
I
FIGURE 8. BLOWERWHEEL PULLEY
3. Turn the puller bar bolts in, alternately, until the
wheel snaps loose on the shaft.
Do not use a screwdriver or
CAUTION
slmllar tool orpry behlnd the
flywheel against the gear case. The gear case
cover Is dle-cast material and will
break If undue
pressure is applied in this manner.
4. Unscrew the puller from the
flywheel, remove the
I F FEELER WILL
ENTER HOLE
BALL HAS
flywheel mountingscrew and washer and pull the
flywheel off the shaft. Take care not to drop the
wheel. A bentor broken fin will destroythe
balance. Always use a steel key for mounting the
flywheel.
FIGURE 9. GEAR COVER ASSEMBLY
10-6
!
ASSEMBLED THE
DIMENSION SHOWN
ON DRAWING WILL
BE AS INDICATED
CAMSHAFT
GEAR
RIGHT
WRONG
C-1107
INSTALLATION OF BALL SPACER
CENTER
SNAP RING
GOVERNOR
CUP
CAMSHAFT
GOVERNOR
FLYBALL
5 BALL GOVERNOR
6 BALL GOVERNOR
8 BALL GOVERNOR
LOCATIONS FLYBALL
CS-1238
FIGURE 10. GOVERNOR CUP DETAILS
GOVERNOR CUP
nwITH the gear cover
removed, the governor cup
cannot be pulled outward or removed without damage.
If the center pin extends out too far, the cup will
not hold
the flyballs properly. If the distance is less than 7/32"
(5.6 mm), (the engine will race, especially at no load)
remove'the center pin and press in a new pin.
canbe
taken off after removing the snap ring from the camshaft
center pin. Catch the flyballs while sliding the cup off
(Figure 10).
Replace with a new part any flyball which isgrooved or
has a flat spot; the ball spacer if its arms are worn or
otherwise damaged; thegear/spacer assembly if loose
on gear hub, and the
governor cup if the race surface is
grooved or rough. The governor cup must be a freespinning fit on the camshaft center pin, but without any
excessive play.
TIMING GEARS
If replacement of either the crankshaft gearorthe
camshaft gear becomes necessary, always install both
gears new.
The camshaft and gear must be replaced as an assembly
Before removing thecamshaft and gearassembly,
remove the cylinder head and valve assemblies. Then
removethe operating plunger for the breaker points and
tappets.
If replacing the ball spacer, be sureto position it so an
arm is lined up with the space on the camshaft gear (if
your camshaft geardoes not have a space in it,
disregard this paragraph). If the ball spacer arm is not
lined up with the space in the camshaft gear, a flyball
can slip into the space and cause engine racing and
governing problems (Figure 10).
To remove the crankshaft gear, first remove the snap
ring and retainer washer, then attach the gear pulling
ring using two No. 10-32screws (Figure 11). Tighten
the screws alternately until both are tight. Attach a gear
puller to the puller ring and proceed to remove the gear.
When installing the governor cup, tilt the engine so the
gear is up, put the flyballs in place (Figure lo), and
install the cup and snap ring on the center pin.
Each timing gear is stamped with "0"
near the edge. The
gearteethmustmesh
so thatthesemarks
exactly
coincide when the gears are installed in the engine.
When installing the camshaft gearand shaft assembly,
be sure that the thrust washer is properly in place
behind the camshaft gear. Then install the crankshaft
retaining washer and lock ring.
The camshaft centerpin extends out 3/4inch (19mm)
from the endof the camshaft. This
distance provides an
in-and-out travel distance of 7/32 inch (5.6mm) for the
governor cup, as illustrated. Hold the cup against the
flyballs when measuring. The camshaft center pin
10-7
CRANKSHAFT
4. Turn the crankshaft until the piston is
at the
bottom of its stroke and remove the connecting
rod nuts. Lift the rod bearing cap from the rod
and
push therod and piston assembly out through the
top of the cylinder usinghammer
a
handle. A v o i d
scratching the crankpin and cylinder wall whel
removing the piston and rod.
GEAR PULLER
5. Mark each piston and rod assembly so they can be
returned to their respective cylinders after overhaul.
Keep connectingrodbearingcapswith
their
respective rods.
6. Remove the piston rings from
the
piston with a
piston ring spreader (Figure 13).Remove the piston
pin retainer and push the piston pin out.
INSTALLING TIMING
FIGURE 11. TIMING GEARREMOVALANDINSTALLATION
PISTONS AND CONNECTING RODS
Observe thefollowingprocedure
when removing
pistons and connecting rods from the
engine.
1. Drain oil.
2. Remove the cylinder head and oil base pan from
the engine.
3. Remove the ridge from the top of each cylinder
with aridge reamer beforeattemptingpiston
removal (Figure 12).
CAUTION cylinder
Forcingthepistonfromthe
before reaming may
cause damage to the piston lands and break
rings.
FIGURE 13. REMOVINGPISTONRINGS
7. Remove dirt and deposits from the piston surfaces
with an approved cleaning solvent. Clean the piston
ring grooves with a groove cleaner or the end of a
piston ring filed to a sharp point (Figure 14). Care
must be taken not to remove metalfrom the groove
sides:
Do not use a caustic cleaning solvent
or wire brushfor cleaning pistons.
These materials will cause piston damage.
CAUTION
When cleaning the connecting rods in solvent, besure
to include the rod bore. Blow out all passages with
compressed air.
Engines that have beenfitted with 0.005 inch (0.13 mm)
oversize pistons at the factory are identified by the letter
E after the serial number. Number is stamped on t h e
cylinder block and on the unit nameplate.
FIGURE 12. REMOVINGRIDGEFROMCYLINDER
10-8
FIGURE 15. CHECKINGRINGSIDECLEARANCE
with deep nicks, signs of fractures, scored
bores or bores out of round more than 0.002
inch.
2. Use a new piston pin to
check connecting rod
for wear. A push fit clearance is required and
varies from engine to engine. If a new piston
pin falls through a dry rod pin bore
as a result
of its own weight, replace the rod.
FIGURE 14. PISTONGROOVECLEANING
Fitting Pistons:
Inspection
1. Proper piston tolerances must be maintained
for satisfactory operation.
Follow the procedures given below when inspecting
pistons and connecting rods.
2. Refer to DIMENSIONS AND CLEARANCES to
determine where to measure piston to be sure
the total clearance follows specifications.
Piston Inspection:
1. Inspect the pistons for fractures atthe
ring
lands, skirts,and pin bosses. Check for wear at
the ring lands using a new ring and feeler gauge
(Figure 15). Replace the piston when the side
clearance of the top compression ring reaches
0.008 inch (0.20 mm).
2. Replace pistons showing signs of scuffing,
scoring, wornring lands, fractures ordamage
from preignition. Excessive piston wear near
theedgeofthetopringlandindicates
preignition.
Connecting Rod Inspection:
1. Replace connecting rod bolts and nuts with
damaged threads. Replace connecting rods
FIGURE 16. MEASURINGPISTONCLEARANCE
10-9
Cleaning
Fitting PistonRings:
After removing pistons, crankshaft, cylinder heads,
etc., inspect block for cracks and extreme wear. If
block is still serviceable, prepare it for cleaning as
follows:
1. Install the piston ring inthe cylinder bore. Invert
the piston and push the ring to the end of ring
travel, about halfway into the bore, which trues
the ring end gap. Check the gap with a feeler
gauge (Figure 17).
1. Scrape all oldgasket material from block.Remove
oil by-pass to allow cleaning solutionto contact
inside of oil passages.
2. The practiceof filing ringends to increase the
end gap is not recommended. If the ring end
gap does not meet specifications, check for
the correct set of rings and the correct bore
size A cylinderborethatis
0.001 inch
(0.03mm) undersize will reduce theend gap
0.003 inch (0.08 mm).
2. Remove grease and scale from cylinder block by
agitatingin a bath of commercialcleaning
solution or hotsoapy washing solution.
3. Rinse block in clean.hot water to remove cleaning
solution.
Inspection
When rebuilding theengine, thoroughly inspect block
for any condition that wouldmake it unfit for further
use. This inspection must
be made after all parts have
beenremovedandblockhasbeenthoroughly
cleaned and dried.
1. Make a thorough check for
cracks. Minute cracks
may be detected by coating the suspected area
with a mixture of 25 percent kerosene and 75
percent light motor oil. Wipe the part dry and
immediately apply acoating of zinc oxide(white
lead) 'dissolved in wood alcohol. If cracks
are
present, the white coating
will become discolored
at the defective area. Always replace a cracked
cylinder
block.
2. Inspect all machined surfaces and threaded holes.
Carefully remove any nicks or burrs from machined surfaces. Clean out tapped holesand
clean up any damaged threads.
3. Check top of block for flatness with a straight
edge and afeeler gauge.
Cylinder Bore Inspection Inspect cylinderbores for
scuffing, 'scratches, wear, and scoring. If cylinder
bores are scuffed, scratched, scored, or worn, they
must be rebored and honed for
the next oversize
piston.
When the appearance of cylinder bores is good and
there are noscuff marks, check cylinder bore wear
for
or out of roundness as follows:
FIGURE 17. POSITIONING OF PISTONRING
AND MEASURING OF END GAP
1, Check cylinder bore for taper, out of round, and
wear with a cylinder bore
gauge, telescope gauge
orinsidemicrometer.Thesemeasurements
should be taken at four places, top and bottom of
piston ring travel, parallel and perpendicular to
axis of crankshaft.
CYLINDER BLOCK
The cylinder block is the main support for allother
basic engine parts. Crankshaft and camshaft are
supported by the block, assuring alignment of the
crankshaft and cylinder bores.
2. Record measurements taken at top and bottom of
piston travel as follows (Figure 18).
10-10
A. Measure and record as “A” the cylinder bore
diameter (parallel to crankshaft)near the top
of cylinderbore where greatest amount of
wear occurs.
TOP END OF CYLlNDER
B. Also measure and record as “B” cylinder bore
diameter (parallel to crankshaft) at the bottom
of piston travel.
RING
WEAR
A REA
C. Measure and record as “C” cylinderbore
diameter (perpendicular to crankshaft) near
thetop
of cylinderbore
where greatest
amount of wear occurs.
0490
I
BOTTOM OF RING TRAVEL
D. Also measure and record as “D” cylinderbore
diameter (perpendicular to crankshaft)at the
bottom of piston travel.
I
E. Reading “A” subtracted from
reading “B” and
reading “C” subtractedfromreading“D”
indicates cylinder taper.
If cylinder taper exceeds
that
specified
in
DIMENSIONS AND CLEARANCES rebore and
hone cylinder to the next oversize.
F. Reading “A” compared to reading “C” and
reading “B”compared to reading “D” indicate
whether or not cylinder is out of round. If out of
round exceeds that specified in DIMENSIONS
AND CLEARANCES thecylinders must be
rebored and honed to the next oversize. A
reboring machine is used whengoing to oversize
pistons.
Reboring the Cylinder
Rebore and hone engine whenever cylinder bore is
worn, damaged, out of round, or if cylinder taper
exceeds specifications. A worn cylinder bore should
be resized to the smallest standard oversize diameter
at which it will clean up. The final finish and bore
diameters should then be obtained by honing. Final
bore diameter should equal the standard diameter
added to the oversize.
FIGURE 18. METHODS OF MEASURINGTHEDIAMETER
OF A CYLINDER BORE
After boring to the correct oversize cylinder bore
dimensionpistonandring
clearance should be
appropriate. There is no need to adjust or “fit” pistons
and rings.
When reboringcylinders,
cautions:
lfboring barisoperatedincorrectly
CAUTION
itwillproduce
a roughcylindersurface that maynot clean up even whenhoned. Boring
take thefollowing
pre-
1. Make,sure cuttingtool is properlygroundbefore
using it.
2. Be sure top of engine block is smooth and deposit
should be done only by qualified service personnel
careful
who are their in
work.
free.
10-1 1
3. Clean base of boring bar before bar is set up.
Deposits underboring bar will cause it to tilt
and
the cylinder will be distorted after boring.
4. Make aninitial rough cut, followed by a cut.
finish
Then hone cylinder bore
to the specifiedoversize.
Deglazing Cylinder Bores
Deglaze the cylinder bores
if there are no scuff marks
and no wear Or out of round beyond specifications
before installing new rings. Deglazing gives a
finish, butdoes not enlarge cylinderdiameter, so the
original pistons withnew rings may still be used.
The reason for deglazing a cylinder is to provide
cavities to hold oil during piston ring
break-in.
1. Wipe cylinder bores witha clean cloth which has
been dipped in clean, light engine oil.
Honing Cylinders (UsingPrecision Hones)
Refer to hone manufacturer's recommended grit size
to produce specified surface finish
of 20 to 40 RMS.
Too rough of a finish will wear out the rings andtoo
smooth of a finish can retard piston ring seating.
1. Position block solidly for either vertical or hori-
zontal honing. Use either a drill press or heavyduty drill which
operates atapproximately 250 to
450 rpm.
2. Use a brushtypedeglazing
toolwith coated
bristle tips to produce
a crosshatch pattern in the
cylinder bore.
3. Use a slow speed drill to drive the deglazing tool.
Move deglazing tool up anddown in cylinder (10 to
12 complete strokes) rapidly enough to obtain a
crosshatch pattern (Figure 19).
2. Follow hone manufacturer's instructions for the
use of oil or lubricanton stones. Donot use
lubricants witha dry hone.
3. Insert honein bore and
adjust stones to fit snugly
to thenarrowestsection. When adjusted correctly, the hone should not shake or chatter in
cylinder bore, but will drag freely up and down
when hone is not running.
4. Connect drillto hone and start drill.
Feel out bore
for highspots, which cause anincreased drag on
stones. Move hone up and down in bore with
shortoverlapping strokes about 40 times per
minute.Usually
bottom of cylindermust
be
worked out first because it is smaller. As cylinder
takes a uniform diameter, move honeup and
down all theway through cylinder bore.
5. Check diameter of the cylinder regularly during
honing. A dial bore gauge is the easiest method
but a telescoping gauge can beused. Check size
at six places in bore; measure twice at top, middle
and bottom at 90-degree angles.
6. Crosshatch formed by the
stones should forman
includedangle
of 23 degrees. Thiscan
be
achieved by moving the rotating hone
(250 to 450
rpm) up and down in cylinder bore
about 40 times
per minute.
7. Clean cylinder bores thoroughly with
soap, water
andclean rags. A clean white rag shouldnot
become soiled on wall after cleaning
is complete.
Do not use a solvent or gasoline since theywash
oil from thewalls but leave the metal particles.
8 . Dry crankcase and coat it with oil.
FIGURE 19. CROSS
HATCHING
...
Never use gasoline or commerCAUTION
cial cleaners to clean cylinder
bores after deglazing or honing. These solvents
will not remove abrasives from the walls. Abrasives not removed from engine will rapidly wear
rings, 'cylinder walls, and bearing surfaces of all
lubricated parts.
4. Clean cylinder bore thoroughly with soap, water
and clean rags. Continue cleaning until a clean
white ragshows
nodiscoloring when wiped
through cylinder bore.
CRANKSHAFT
C l e a n crankshaft thoroughly and inspect journals for
scoring, chipping, cracking, or signs of overheating. If
crankshaft has overheated, is scored, or excessively
worn, reconditioning or replacement will be required.
Examine bearing journals for cracks if overheating has
occurred.
ALIGN HOLE IN BEARING
Measure crankshaft main bearing and connecting rod
journals at several places on their diameter to check for
roundness and taper.
7/32”(5.6 mm)
FROM OUTSIDE
IN BEARING
BORE
CAMSHAFT BEARlNG
The only recommended method of reconditioning the
crankshaft is regrinding, as required to accommodate
undersize bearings. Metallizing of bearing journals is
not recommended.
FIGURE 20. FRONTCAMSHAFTBEARING
Replacement camshaft bearings are precision type
whichdo not require line reaming or lineboring after
installation. Clean outside of the bearing and bearing
bore in the block. Before installing cam bearings use
[email protected] Mount on outside diameter of bearing.
Use a combination bearing driver to install bearings.
Place the bearing on the crankcase Over the bearing
bore with the lubricating
hole
(front only) in the proper
position. Be sure to start the bearing straight. Press in
the front bearing flush with the outside end of the
bearing bore. Front cam bearing oil hole must line up
with oiling hole in cylinder block (Figure 20). Press in
the rear camshaft bearing until past the ignition plunger
hole. Lubricate bearing surfaces with oil after installing.
If regrinding of crankshaft Journals is necessary the
work should be done by a reputable machine shop that
has suitable equipment to handle precision work of this
type. Undersize main bearings are available in sizes of
0.010, 0.020,and 0.030inch. Undersize connecting
rods are available in sizes of 0.010, 0.020, 0.030 and
0.040 inch.
Whenever making major repairs on the engine, always
inspect the drilled passagesofthecrankshaft.Clean
them to removeany foreign material and to assure
p r o p e r lubrication of the connecting rods.
New crankshaft main bearings areprecision type which
do not requirelinereamingorlineboring
after
installation. Use a press or a suitable driver to remove
bearings. Support casting to avoid distortion and to
avoid damaging the bearing bore during removal and
installation.
Before installing main bearings,expand bearing bore by
placing’ the
casting in an oven heated to 2 0 0 F (94°C). If
practical, cool the precision bearing to shrink it.
BEARINGS
Before installing the front main bearing, use the towelette
included with the bearing kit to clean the outside of the
bearing and bearing bore in the block.
With camshaft and crankshaft removed, use a micrometer to measure diameter of bearing journals. Use a
dial bore gauge or a telescopic gauge and micrometer
to measure inside diameter of bearings. Refer to
DlMENSlON AND CLEARANCE to determine if clearances are within specifications.
Breathing vapor from towelette and
CAUTION
prolonged contact with skin can be
harmful.Be sure area is well ventilated.
After allowing three to four minutes fordrying, apply the
Locktitefrom the small tube to themating surfaces of the
bearing and the bearing bore. Align the oil holes in the
bearing with the oil holes in the bearing bore (Figure 22).
The oil passage should be at least halfopen. Install the
bearing flush with the block, using the combination
driver. Wipe off excess Locktite around the bearing.
Allow at leastonehourforhardeningatroom
temperature.
Any bearing that is scored, chipped, pitted or worn
beyond the specified limits must be replaced.
Removal of the camshaft bearings requires complete
disassembly of the engine: Use a press or a suitable
driver to remove bearings. Support casting to avoid
andto avoid damaging the bearing bore
during removal and installation.
10-13
REAR BEARING END PLATE
LOCK PIN
In the rear bearing plate, install the bearing flush to
1/64 inch (0.40 mm) below the endof the bore. Be sure
to alignthe oil holes in the bearing with the oil holes in
the bearing bore (Figure 21). The oil passage must be
least half open. Lubricate bearing after installation.
If head of lock pin is damaged, use side cutters or Easy
Out tool to remove and install new pin. Oil grooves in
thrust washers must face the crankshaft, and washers
must be flat (not bent). The two notches on each washer
must fit over the two lock pins to prevent riding on the
crankshaft (Figure 21).
FIGURE 21. BEARINGS FOR REARBEARINGPLATE
Engines shipped from the factory have
separate
thrust
washers and main bearings for both front and rear of
engine’ Front bearing replacement part is a One piece
bearing (with attached thrust washer)as shown in
Figure 22.Do not add an additional thrust washer to this
front bearing.
Lubricate the front main bearing lightly with oil and
insert the crankshaft. With the rear
bearing plate gasket
in place and the rear plate bearing lubricated, slide the
thrust washer (grooves toward crankshaft) and plate
over the end of the crankshaft. Line up notches of thrust
washer with lock pins before tightening end plate or
lock pins will be damaged.
CRANKSHAFT ENDPLAY
After the rear bearing end plate has been tightened,
usingthetorquerecommendedin ASSEMBLY TORQUES
AND SPECIAL TOOLS,check the crankshaft endplayas
shown in Figure 23. If there is too much endplay (see
DIMENSIONSANDCLEARANCES for minimum and
maximum endplay), removethe rear bearing end plate
and add a shim (Figure 21) between thethrust washer
and plate. Reinstallthe end plate, making sure the thrust
washer and shim notches line up with the lock pins.
Torque and recheck endplay of the crankshaft.
FRONT MAIN
BEARING BORE
ALIGN BEARING
LOCK PINS
AND MATCH
OIL HOLES
REPLACEMENT
FRONT MAIN
BEARING
MEASURE ENDPLAY HERE
(REFER TO DIMENSIONS
AND
CLEARANCES)
FIGURE 23. CRANKSHAFTENDPLAY
FIGURE 22. FRONTBEARINGINSTALLATION
10-14
CHECKING CONNECTING ROD BEARING
CLEARANCE WITH PLASTIGAUGE
1. Make certain that all parts are marked or identified
so that they are reinstalled
in their original positions.
Using aclean dry cloth, thoroughly clean all oilfrom
crankshaft journal and connecting rod.
2. Place a piece of correct sizePlastigauge in the
bearing capthe full width of thejournal surface and
about 1/4 inch (6.35 mm) off center (Figure 24).
3. Rotate the crankshaft about 30 degrees from bottom
dead center and reinstall the bearing cap; tighten
rod bolts to the torque specified in ASSEMBLY
TORQUES AND SPECIAL TOOLS. Do not turn the
crankshaft.
4. Remove bearing cap. The flattened Plastigauge
will
befound adhering to eitherthe bearing capor
crankshaft.
FIGU’RE 24.
MEASURINGBEARINGCLEARANCE
OIL SEALS
5. Compare flattened Plastigauge with the graduations The bearing plate must be removed to replace the oil
on Plastigauge envelope to determine clearance.
seal (Figure 25). Drive the oil seal out from the inside.
Before installing seals, fill the space betweenlips with a
multi-purpose grease. This will improve sealing.
The numberwithin the matching graduation on the
envelope indicates total clearance in millimetres or
thousandths of an inch.
When installing the gear cover oil seal, tap the seal
inward until is
it .645 inch (16.4 mm) fromthe front of the
gear cover.
When installing the bearing plate oil seal, tap the seal
into the bearing plate bore to bottomagainst
the
shoulder in the
plate bore. Use a seal expander
or place
a piece of heavy paper around
the end of the crankshaft,
when replacing the bearing
plate to avoid damaging the
seal. Removethe paper as soon as
the plate is in place.
REAR BEARING PLATE
THIS SURFACE SHOULD BE
CLEANED OF ALL OLD
SEALING COMPOUND
BEFORE INSTALLING SEAL.
MOUNTING FACE
OF GEAR COVER
FRONT
DRIVE OR PRESS OIL
SEAL TO SHOULDER
OF THE PLATE BORE
GEAR COVER
THIS GEAR COVER SURFACE
SHOULD BE CLEANED OF ALL
OLD SEALING COMPOUND
BEFORE INSTALLING SEAL.
REAR BEARING PLATE
OIL SEAL
GEAR COVER OIL SEAL
FIGURE 25. GEAR
COVER
AND
REAR
BEARING
PLATE
OIL SEALS
10-15
-1163
PISTON ASSEMBLY
Lubricate all parts with engine oil.
Position piston on its respective rod andinstall the
pin.
OIL HOLE
TOWARD
CAMSHAFT
Install the rings on thepiston’s starting with the oil
control ring (Figure 26). Use apiston ring spreader
to prevent twisting or excessive expansion of the
ring.. Compression rings have a dot or the word
“top” on one side
of the ring to
indicate which side
faces the topof the piston. Unmarked piston rings
can beinstalled either way. Theoil control ring has
anexpander; install theexpander first andthen
close until the expander ends butt. The
joint should
be 180 degrees from the gapof that ring.
CT-1077
FIGURE
26. PISTONRINGS
INSTALLATION OF PISTON IN CYLINDER
1. Turn the crankshaft
to position the number onerod
FIGURE 27. INSTALLINGPISTONAND
CONNECTING ROD
bearing journal at the bottom of its stroke.
2. Lubricate the numberone piston assembly and
5. The bearing capmust be tapped to properlyalign it
with therest ofthe connectingrod. Clearance varies
on the journal if this
notis
done.
inside of the cylinder. Compress the rings with a ring
compressor (Figure 27).
3. Position the piston and assembly
rod
in the cylinder
block. Notched side of connecting rod must face
camshaft; rod bolts must be off-set toward outside
of block.
6. Install the remaining piston and rod in thesame
manner. Crankthe engineover byhand tosee that
all bearingsare free.
7. Install the oil base with a new gasket.
4. Tap the piston downinto the bore with the handle
end of a hammeruntil the connecting rodseated
is
on thejournal (Figure 27). Install the bearing cap on
the rod. Install and tighten the nutsevenly, in steps,
to thespecified torques.
lQl6
8. Install thecylinder
heads.See
Cylinder H e a d
section for torques andtorquing procedure.
9. Replace oil andbreak in engine.
CYLINDER HEADS
,Remove the cylinder heads for lead cleaning and
gasket change at least every 250 hours, or when poor
engine performance is noticed.
1. Use a 1/2 inch (13 mm) socket wrench to remove
cylinder head nuts. Lift heads off.
6. Follow the head torque sequence shown in Figure 29 tightening all nuts to 5 ft-lbs (7 Nm), then
10 ft-lbs (14 Nm), then to the torque specified in the
ASSEMBLY TORQUESsection. Recheck all nuts for
correct torque.
not torque or
remove heads
CAUTION Do
when they
are
hot. Warpage
may occur. The gasket surface must be below
100" F before removal. At temperatures above
100" F, the gasket will become gummyand difficult toremove from the surface of the block and
cylinder head.
2. After removing heads, clean out allcarbon deposits. Be careful not to damage the outer sealing
edges where gaskets fit. The heads are made of
aluminum and can be damaged by careless
handling.
3. Use new head gaskets and clean both the heads
and thecylinder block thoroughly
where the head
gaskets rest.
4. Place a head gasket on the cylinder head and
align the stud holes in the gasket with the stud
holes in the cylinder head. While holding the
gasket against the cylinderhead, carefully install
the cylinder head on the engine. Do not attempt
to slide the gasket over the studs without the
cylinder head behind it or thegasket may tear.
-f
5. Install a flat washer, two compression washers,
and nuton each of the topsix studs(see Figure28
for correct sequence). When properly installed,
only the outside
edges of the compressionwashers will be in contact witheach other. Install a flat
washer and nut on each of the four bottom studs.
LEFT CYLINDER
RIGHT CYLINDER
FIGURE 29. HEADBOLTTIGHTENINGSEQUENCE
Too much torquewill flatten the
CAUTION compression
washersand could
result in engine damage.
7. Recheck torque before engine has run a total of
50 hours.
HEAT TREATED
not torque or
remove heads
CAUTION Do
when they are hot. Warpage
COMPRESSION
WASHERS
.HARDENED
WASHERS
HEAD
GASKET
6 LONG STUDS/HEAD
4 SHORT STUDS/HEAD
FIGURE 28. CYLINDERHEAD WITH COMPRESSION
WASHERS
may occur. The gasket surface mustbe below
100F before removal. At temperatures above
100" F, the gasket wlll become gummy and dlfficult toremove fromthe surface of the block and
cylinder head.
CYLINDER HEAD STUD TEST
AND REPLACEMENT PROCEDURE
This cylinder head stud replacement procedure should
be used whenever replacing any of thetop six studs on
the block. The use of Helicoil is not a recommended
repair procedure. If aHelicoil has been used, the
cylinder block must be replaced. Graphoil head and
intake manifold gaskets should also be used when
replacing cylinder head studs.
HEAT TREATED
NUTS
COMPRESSION
WASHERS
Parts Required
Part No.
520-0912
110-2987
154-2219
420-0398
Description
Step stud
Head gasket
Intake
manifold
Drilling
fixture
HARDENED
WASHERS
gasket
(Reusable tool)
HEAD
GASKET
6 LONG STUDS (TOP)
4 SHORT
STUDS
(BOTTOM)
1. Disconnect the spark plug wires and remove the
spark plugs and cylinder head air shrouds from
each cylinder.
TORQUE TOP SIX NUTS
TO 12 LB-FT.(COLD)
2. Remove the nuts and compression washers (do not
remove the flatwashers) from the top six studs on
each cylinder head (Figure 30). Each stud will have
two compression washers andone flatwasher
arranged in the sequence shown in Figure 31.
TORQUE BOTTOM FOUR
NUTS TO 15 LB-FT.
FIGURE 31. CYLINDERHEADSTUDS
Do not remove thenuts from the bottom four studs
before the testprocedure is completed.
3. Replace the nuts and
then test the topsix cylinder
head studs by tightening (use
an accurate torque
wrench) each nut to 30 ft-lb (40 Nm) of torque.
Make a note of anystuds that cannotbe tightened
to 30 ft-lb of torque.
USE STUDS SHOWN ABOVE LINE
FOR SECTION 1 STUD TEST
4. Remove thecylinder-headnuts,flatwashers,
cylinder head, and head gasket. Discard thehead
gasket and remove any studs that could not be
torqued to 30 ft-lb (40Nm) without thread pull
out.
LEFT
CYLtNDER
5. Examine the gasket surfaces of the block and
cylinder head for distortion or irregularities that
could cause leakage. Check the head and block
for warpage by laying a straight edge over the
length of the gasket surface. If a0.005 inch feeler
gauge fits between the straight edge and gasket
surface, the partmust be replaced or milled flat.
A
maximum of0.010 inch may be machined from
the cylinder block orhead.
RIGHT CYLINDER
NUMBERS INDICATE CORRECT
TIGHTENING SEQUENCE FOR
CYLINDER HEAD NUTS
FIGURE 30. CYLINDERHEADS
-10-18
On some engines, it is possible that groove
a
from
the old head gasket fire ring may be impressed
into thehead and/or block. If this is the case, it is
essential thatthe part be replaced or milled to
remove the imperfection.
If all of the top six studs accepted 30 ft-lb of
torque without pulling out,the new head gasket
may be put on without
replacement of the studs. If
this is thecase, skip steps 6 through 12.
14. Blow out all residual debris andmetal chips using
low pressure (35 PSI or less) air. If a hole was
drilled intoeither theexhaust or intake port,
open
the valve on that port and blowit out thoroughly.
Replace manifold if removed during the drilling
and tapping operations.
ARROWS INDICATE STUDS TO
USE FOR ATTACHING FIXTURE
6. Fit the special repair fixture (Onan Tool #420-0398)
to the surface of the block. Use the studs shown in
Figure 32 and two cylinder head nuts to secure
fixture to head of block.
Some applications may require that three or four
flatwashers be placed over the studs between the
block and fixture to space the fixture away from the
block. This will be necessary if the fixture does not
clear the sheet metalscroll backing plate.
7. Insert the small size
bushing into the fixture over the
hole(s) with damaged threads and lock it in place.
With the bushing as a guide, drill out the damaged
threads using a 27/64size drill bit. If drilling out the
holes on the SIDE of the block, drill through to the
fourth fin (Figure 33). If drilling out the holes at the
TOP of the block, it will be necessary to remove the
corresponding intake or exhaust manifold. The
drill
bit should penetrate completely into the port but
should not contact the opposite wall of the port
(Figure 33).
c-1009
FIGURE 32. REPAIRFIXTURE
INTAKE PORT
8. Replace the small bushing with
the large bushing
and lock intoplace. Using a1/2-13 tap, carefully
formthe threads, making sure there are full
threads the entire lengthof the hole.
9. After all drilling and tapping
is completed, remove
the special fixture andrepeat the same operation
on theother cylinder if necessary.
10. Remove the ridge around all new holes using a
flat file or a 45" chamfertool. When usinga
chamfer tool, the depthof thechamfer shouldbe
1/32 to 1/16 inch deep.
11. Apply screw thread retaining compound (Locktite 242) to the large end of each new step stud.
Installthe stepped replacement stud,making
suretheentire
stepped portion is belowthe
gasket surface.
12. When putting a stepped stud into the hole that
penetrates into theexhaust port, it will be necessary to
cut
approximately 3/16 to
1/4
inch
(3
threads) off the stepped portion of the stud. No
part of this studmay extend into the exhaust port
or itwillinterferewiththe
exhaust manifold
assembly.
13. Turn engineso that both valves are closed. Using
aflat scraper and/or wire brush, remove all lead
and carbon deposits from the top of the piston,
valve area, and cylinderhead combustion chamber.
c-I010
FIGURE 33. DRILLINGPROCEDURE
10-19
ALIGNING BLOWER WHEEL, VENTURI
AND CHAFF SCREEN
It may be difficult to line up thescrew holes in the
blower housing chaff
screen with thosein the venturi
andthose in the blower wheel if these parts are
separated without noting their
relative positions.The
holes will match up if the
parts are aligned as shown
in Figure 34.
SCREW HOLES ALIGN
THROUGH PART DIAMETER
BLOWER WHEEL
SCREW HOLES ALIGN
THROUGH PART DIAMETER
VENTURI
CHAFF SCREEN
POSITION PARTS WITH ALIGNED
SCREW HOLES AT TOP
FIGURE 34. BLOWERWHEEL,VENTURIANDCHAFF
SCREEN ALIGNMENT
10-20
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