EX13, 17, 21, 27 ENGINES
SERVICE
MANUAL
Models
EX13, 17, 21, 27
ENGINES
PUB-ES1934
Rev. 10/05
940 Lively Blvd. • Wood Dale, IL 60191 • Phone: 630-350-8200 • Fax: 630-350-8212
e-mail: sales@robinamerica.com • www.robinamerica.com
© Copyright 2005 Robin America, Inc.
CONTENTS
Section
Title
Page
1. SPECIFICATIONS ...................................................................................................... 1
2. PERFORMANCE ...................................................................................................... 2
3. FEATURES ............................................................................................................... 7
4. GENERAL DESCRIPTION OF ENGINE COMPONENTS ........................................ 8
5. DISASSEMBLY AND REASSEMBLY .................................................................... 14
5-1 PREPARATIONS AND PRECAUTIONS ............................................................ 14
5-2 SPECIAL TOOLS .............................................................................................. 14
5-3 DISASSEMBLY PROCEDURE .......................................................................... 15
5-4 REASSEMBLY PROCEDURE ........................................................................... 29
6. ENGINE OIL ........................................................................................................... 47
7. MAGNETO .............................................................................................................. 48
8. WIRING DIAGRAM ................................................................................................. 51
9. ELECTRIC STARTER ............................................................................................. 53
10. OIL SENSOR .......................................................................................................... 55
11. AUTOMATIC DECOMPRESSION SYSTEM ........................................................... 56
12. CARBURETOR ....................................................................................................... 57
13. RECOIL STARTER ................................................................................................. 61
14. INSTALLATION ...................................................................................................... 66
15. TROUBLESHOOTING ............................................................................................ 68
16. STANDARD REPAIR TABLES ............................................................................... 74
15-1 STANDARD DIMENSIONS AND LIMITS OF USE ........................................... 74
15-2 TIGHTENING TORQUE .................................................................................... 80
17. MAINTENANCE AND STORAGE .......................................................................... 81
1. SPECIFICATIONS
Model
EX13D
EX17D
EX21D
EX27D
Air-Cooled, 4-Cycle, Slant Single-Cylinder,
Horizontal P.T.O. Shaft, OHC Gasoline Engine
Type
Bore & Stroke
mm
(in.)
Piston Displacement
ml
(cu.in.)
58 x 48
(2.28 x 1.89)
67 x 48
(2.64 x 1.89)
67 x 60
(2.64 x 2.36)
75 x 60
(2.95 x 2.36)
126
(7.69)
169
(10.31)
211
(12.87)
265
(16.17)
Compression Ratio
8.5
8.3
Continuous Output
kW(HP)/r.p.m.
1.9(2.6)/3000
2.2(3.0)/3600
2.6(3.5)/3000
2.9(4.0)/3600
3.2(4.4)/3000
3.7(5.0)/3600
4.4(6.0)/3000
5.1(7.0)/3600
Maximum Output
kW(HP)/r.p.m.
3.2(4.3)/4000
4.2(5.7)/4000
5.1(7.0)/4000
6.6(9.0)/4000
Maximum Torque
N・m / r.p.m.
(kgf・m / r.p.m.)
(ft・lb. / r.p.m.)
8.1/2500
(0.83/2500)
(6.01/2500)
11.3/2500
(1.15/2500)
(8.34/2500
13.9/2500
(1.41/2500)
(10.26/2500
18.6/2500
(1.9/2500)
(13.74/2500
Direction of Rotation
Counterclockwise as viewed from the P.T.O. shaft side
Valve Arrangement
Overhead cam system
Cooling System
Forced air cooling system
Lubrication System
Splash lubrication system
Automobile engine oil ; Grade SE or higher (SG,SH or SJ in recomended)
SAE 10W-30-----Under ordinary atmospheric temperatures
SAE 5W-30-------In cold areas
Lubricant
Capacity of Lubricant
L
0.6
Carburetor
Horizontal draft, Float type
Fuel
Fuel Consumption Rate
Automobile unleaded gasoline
g/kW・h
(g/HP・h)
367 (270) at continuous rated output
Fuel Supply System
Fuel Tank Capacity
Gravity type
L
2.7
3.6
Ignition System
6.1
Transistorized magneto
Spark Plug
Charging Capacity
(Option)
1.0
NGK BR-6HS (CHAMPION RL86C)
V-A
Starting System
-------------
12-1A, 3A, 16.7A (Option)
Recoil starter
Recoil starter / Electric starter (Option)
Governor System
Centrifugal flyweight system
Dry Weight
kg
(lb.)
Dimensions (L x W x H)
mm
(in.)
14
(30.87)
15
(33.08)
297 x 341 x 318 304 x 354 x 335
(11.7x13.4x12.5) (12.0x13.9x13.2)
* Specifications are subject to change without notice.
- 1-
16
(35.28)
21
(46.31)
311 x 366 x 335
(12.2x14.4x13.2)
351 x 420 x 410
(13.8x16.5x16.1)
2. PERFORMANCE
2-1 MAXIMUM OUTPUT
The Maximum output is the output of an engine with its throttle valve fully opened and considering that all the
moving parts are properly broken in.
A new engine may not produce full maximum output while its moving parts are still not broken-in.
NOTE :
Power curves shown in the following charts are made in conformity with SAE internal combustion engine standard
test code J1349.
2-2 CONTINUOUS RATED OUTPUT
The continuous rated output is the output of an engine at optimum governed speed which is most favorable from
the view point of engin’s life and fuel consumption.
When the engine is installed on a certain equipment, it is recommended that the continuous output required
from the equipment to be kept below this continuous rated output.
2-3 MAXIMUM TORQUE
The maximum torque is the torque at the output shaft when the engine is producing maximum output at a
specific r.p.m..
- 2-
2-4 PERFORMANCE CURVES
EX13D
9.0
8.0
MAXIMUM TORQUE
kW
4.0
[HP]
5.0
3.5
MAXIMUM HORSEPOWER
4.0
3.0
2.5
OUTPUT
3.0
2.0
CONTINUOUS
RATED HP
2.0
1.5
RECOMMENDED
HORSEPOWER
RANGE
1.0
1.0
0.5
0
0
2000
2400
2800
0.8
0.7
TORQUE
7.0
0.9
3200
REVOLUTION
- 3-
3600
r.p.m.
4000
EX17D
11.0
10.0
MAXIMUM TORQUE
9.0
kW
[HP]
6.0
4.5
MAXIMUM HORSEPOWER
4.0
5.0
3.5
4.0
3.0
2.5
CONTINUOUS
RATED HP
OUTPUT
3.0
2.0
RECOMMENDED
HORSEPOWER
RANGE
2.0
1.5
1.0
1.0
0.5
0
0
2000
2400
2800
REVOLUTION
- 4-
3200
3600
r.p.m.
4000
1.2
1.1
1.0
0.9
TORQUE
12.0
EX21D
14.0
13.0
MAXIMUM TORQUE
12.0
kW
5.5
[PS]
7.0
5.0
MAXIMUM HORSEPOWER
4.5
6.0
4.0
5.0
3.5
OUTPUT
4.0
3.0
CONTINUOUS
RATED HP
2.5
RECOMMENDED
HORSEPOWER
RANGE
3.0
2.0
2.0
1.5
1.0
1.0
0.5
0
0
2000
2400
2800
3200
REVOLUTION
- 5-
3600
r.p.m.
4000
1.5
1.4
1.3
1.2
TORQUE
15.0
EX27D
18.0
MAXIMUM TORQUE
[HP]
9.0
kW
7.0
1.7
16.0
1.6
15.0
1.5
6.5
6.0
5.5
7.0
6.0
5.0
4.5
CONTINUOUS
RATED HP
4.0
5.0
OUTPUT
3.5
4.0
RECOMMENDED
HORSEPOWER
RANGE
3.0
2.5
3.0
2.0
2.0
1.5
1.0
1.0
0.5
0
0
2000
2400
2800
REVOLUTION
- 6-
3200
3600
r.p.m.
1.8
17.0
MAXIMUM HORSEPOWER
8.0
1.9
4000
TORQUE
19.0
3. FEATURES
3-1 EXTREMELY SILENT - SOFT TONE QUALITY
EX engines are 2dBA quieter and softer in tone than other engines in the same class.
This quiet and soft tone is achieved by:
- A reduction in mechanical noise realized by employing sophisticated OHC system.
- Employment of an optimized capacity Rigid Muffler.
3-2 EXTREMELY EASY START - NO KICK-BACK
Reliable Starting and Less Pulling Force are achieved by:
- Sophisticated Mechanical Compression Release System as well as newly designed Combustion Chamber.
- EX engines start instantly even at minus (-) 10°
C, without any perceptible kick-back.
3-3 EXTREMELY EASY MAINTENANCE
Extreme ease of maintenance is realized by:
- High Parts Commonality
simplifies maintenance & lowers repair cost due to fewer parts for service.
More than 90% of component parts are in common between more than two models, in such as Muffler,
Intake and Exhaust Valves, Valve Springs, etc.
Furthermore, more than 50% of component parts are in common among EX13, EX17 and EX21, in
such as Chain Guide, Air Cleaner, Ignition Coil, etc.
- Only with ordinary tools, routine maintenance, assembly and disassembly can be performed.
3-4 EXTREMELY ADVANCED TECHNOLOGY
Extreme reliability and durability are achieved by:
- Heavy Duty Chain Driven OHC System
Oval type case-hardened steel links enhance performance and resist stretching, which result in extended
maintenance free operation.
- Completely New Main Bearing Cover’s Design
Flush-mounted main bearing cover with lower moment of deformation significantly increases reliability and
engine life.
- Superior Cooling and Lubrication System
Heat reduction is achieved by more efficient, larger and more numerous cooling fins on crankcase, cylinder
and mounting base, as well as by outstanding oil delivery system.
- Large Ball Bearings on both ends of crankshaft for maximum stability under demanding loads.
- Cast Iron Cylinder Liner resists wear
3-5 EXTREME POWER AND PERFORMANCE
Extremely Higher Power and Lower Fuel Consumption are realized by:
- High speed and homogeneous combustion achieved by sophisticated Pentroof Combustion Chamber which
includes Intake and Exhaust Valves located at optimum angle.
- Straight Intake Port with minimal air flow resistance.
Environmentally friendly
EX engines comply with EPA Phase 2 and CARB Tier II Emission Regulations in the USA.
Extreme application compatibility
With four versatile models, existing slant-cylinder engines can be easily replaced.
- 7-
4. GENERAL DESCRIPTION OF ENGINE COMPONENTS
4-1 CYLINDER AND CRANKCASE
The cylinder and crankcase are aluminum die-casting
as a single piece. A special cast iron cylinder liner is
molded into the aluminum die-casting.
The crankcase has a mounting surface on the output
shaft side to which the main bearing cover is attached.
The cylinder is inclined to the right at an angle of 25
degrees from the horizontal as viewed from the output
shaft side.
Fig. 4-1
4-2 MAIN BEARING COVER
The main bearing cover is an aluminum die-casting,
which is mounted on the output shaft side of the
crankcase. By removing the main bearing cover, the
inside of the engine can be inspected with ease. Pilots
and bosses are machined into the cover to facilitate the
direct coupling of the engine with machines such as
generators and pumps. There is an oil filling port, with
oil gauge, on either side of the cover.
Fig. 4-2
4-3 CRANKSHAFT
The crankshaft is made of spheroidal graphite cast iron,
and the crank pin is high-frequency induction-hardened.
The crank sprocket used to drive the chain and the
gear used to drive the governor gear are pressed into
the output end of the shaft.
Fig. 4-3
4-4 CONNECTING ROD AND PISTON
The connecting rod is a specially heat-treated aluminum
alloy die-casting. Its large and small ends function as
bearings. A splasher built into the connecting rod
lubricates by splashing engine oil. The piston is an
aluminum alloy casting with grooves for mounting two
compression rings and one oil ring.
Fig. 4-4
- 8-
4-5 PISTON RINGS
The piston rings are made of special cast iron. The profile of the top ring is a barrel face or tapered face, and
that of the second ring is a tapered face. There are 2 types of oil ring depending on the engine specification.
As those are interchangeable, the cutter ring with coil expander type can be selected as the spare part.
1
1
TOP
RING
BARREL
(EX13/27)
TAPER
(EX17/21)
2
3
2
3
SECOND
RING
OIL
RING
TAPER
CUTTER RING
WITH COIL
EXPANDER
THREE-PIECE
CONSTRUCTION
Fig. 4-5
4-6 CAMSHAFT
The camshaft and the sprocket are made of special
sintered alloy. They are constructed as a single piece.
The camshaft is provided with intake and exhaust cam,
and the decompression release lever is mounted on
the sprocket shaft end side.
Fig. 4-6
4-7 VALVE ARRANGEMENT
EXHAUST VALVE
This engine has a chain-driven overhead cam and
overhead valve construction, with a single cam
performing both intake and exhaust operations.
Fig. 4-7
4-8 CYLINDER HEAD
The cylinder head is an aluminum die-casting with a
pent roof combustion chamber construction. The intake
and exhaust ports are arranged in a cross direction to
improve combustion efficiency.
Fig. 4-8
- 9-
INTAKE VALVE
4-9 GOVERNOR SYSTEM
GOVERNOR GEAR
This engine is equipped with a centrifugal flyweight type
governor that makes it possible to operate the engine
at a constant speed, even with load variations. (The
governor flyweights are mounted on a governor gear.)
Fig. 4-9
4-10 COOLING SYSTEM
The engine uses a forced air-cooling system in which a cooling fan (which also works as a flywheel) forces
cooling air into the cylinder and the cylinder head. Baffles are provided to guide the flow of the cooling air.
(Model EX21 is provided with a synthetic resin cooling fan that is separate from the flywheel.)
4-11 LUBRICATION SYSTEM
The rotating parts, sliding parts and valves of the engine
are lubricated with oil in the crankcase. The oil is splashed
onto the parts by the oil splasher on the connecting rod.
4-12 TIMING CHAIN
Timing chain system is adopted and designed for
lubricating for the upper portion of cylinder head.
The timing chain is engaged between the sprocket
portion of integrated camshaft in the cylinder head and
the crankshaft gear sprocket.
The sprocket teeth in particular shape are adopted to
enhance the durability and to realize low noise level.
TIMING CHAIN
OIL SPLASHER
Fig. 4-10
4-13 IGNITION SYSTEM
The ignition system is a transistor controlled magneto
system with the ignition timing set at 23 degrees (EX13/
17/21)[27 degrees (EX27)] before the top dead center.
The magneto consists of a flywheel and ignition coil.
The flywheel (which also works as a fan) is directly
mounted on the crankshaft and the ignition coil is
directly mounted on the crankcase.
※ Model EX13,17,21 and 27D has a smooth advanced
ignition timing system to improve starting performance.
(For further details, refer to page 48, section
IGNITION COIL
FLYWHEEL
“7. MAGNETO”.)
Fig. 4-11
- 10 -
4-14 CARBURETOR
The engine is equipped with a horizontal draft
carburetor. The carburetor setting is calibrated after
careful testing for optimum all-round performance
(including starting, acceleration, fuel consumption,
output power characteristics). Special attention is also
paid to the general-purpose use of the engine. (For
further information, refer to page 57, section “11.
CARBURETOR”.)
Fig.4-12
STD Type
4-15 AIR CLEANER
The engine uses an air cleaner that is quieter than
Dual Element Type
CLEANER
COVER
conventional ones. A semi-wet urethane foam element
CLEANER
COVER
is used in the STD air cleaner. Dual element air cleaner
(with a primary element of dry type sponge and
secondary element of dry type paper) and other types
URETHANE
FOAM
are also provided as special options.
PAPER
ELEMENT
URETHANE
FOAM
Fig.4-13
4-16 BALANCER
(PROVIDED ONLY IN MODEL EX27D)
Unbalanced inertia force is cancelled by the balancer
which rotates at the same speed as the crankshaft to
effectively reduce vibration.
Fig.4-14
RETURN SPRING
4-17 DECOMPRESSION SYSTEM
ROCKER ARM
(EXHAUST VALVE SIDE)
The automatic decompression system is mounted on
the camshaft. It opens the exhaust valve before the
compression top, thereby alleviating the compression
pressure and reducing the force required to pull the
recoil starter.
During engine operation, the decompression system is
overpowered by centrifugal force and compression is
EXHAUST
VALVE
fully utilized to produce power.
CAMSHAFT
Fig.4-15
- 11 -
4-18 SECTIONAL VIEW OF THE ENGINE
Cross sectional view – across the shaft
TANK CAP
FUEL TANK
GOVERNOR SHAFT
BLOWER HOUSING
GOVERNOR LEVER
GOVERNOR GEAR
CRANKSHAFT
CONNECTING ROD
STARTING PULLEY
RECOIL STARTER
FLYWHEEL
CHARGE COIL
(OPTION)
OIL SENSOR
(OPTION)
Fig. 4-16
- 12 -
MAIN BEARING COVER
Cross sectional view – along the shaft
FUEL STRAINER
GOVERNOR LEVER
PISTON
CHAIN GUIDE
MUFFLER
MUFFLER COVER
EXHAUST
VALVE
TAIL SCREEN
or DEFLECTOR
(OPTION)
FUEL TANK
SPARK
ARRESTER
(OPTION)
GOVERNOR
GEAR
MAGNETIC
SWITCH
ROCKER
ARM
CAMSHAFT
INTAKE VALVE
TIMING
CHAIN
PISTON PIN
PISTON RING
STARTING
MOTOR
(OPTION)
TENSIONER
OIL GAUGE
FILLER PLUG
CONNECTING ROD
OIL DRAIN PLUG
CRANKCASE
CRANKSHAFT
OIL SENSOR
(OPTION)
Fig. 4-17
- 13 -
5. DISASSEMBLY AND REASSEMBLY
5-1 PREPARATIONS AND PRECAUTIONS
(1) When disassembling the engine, memorize the location of each part so that you can reassemble the engine
correctly. If necessary, attach identification tags with the required assembly information to the parts.
(2) Store groups of parts in separate boxes. This will make reassembly easier.
(3) To prevent parts from being mislaid, keep each group provisionally assembled after removing the parts from
the engine.
(4) Handle the disassembled parts with the utmost care. Clean them with cleaning oil if necessary.
(5) Use the correct tools in the correct way when disassembling and reassembling the engine.
5-2 SPECIAL TOOLS
Commercially available product
Tool name
Use
Flywheel puller
For pulling off the flywheel
FLYWHEEL PULLER
Fig. 5-1
- 14 -
5-3 DISASSEMBLY PROCEDURE
Step
1
Parts to remove
Drain the engine oill
Remarks and procedures
(1) Remove a drain plug (M14×12mm)
located on both sides of the case.
Take care not to lose the gaskets.
(2) To discharge oil quickly, remove the oil
guage.
Fasteners
14 mm spanner
OIL GAUGE
GASKET
STEP 1
GASKET
DRAIN PLUG
Fig. 5-2
- 15 -
Step
Parts to remove
Remarks and procedures
Air cleaner cover
Remove the air cleaner cover.
Air cleaner
Remove the element, and remove the air
cleaner while pulling the breather pipe away
from the rocker cover.
Fasteners
2
3
STD TYPE
10 mm box spanner
M6 nut: 2 pcs.
M6 × 20 : 1 pc.
DUAL ELEMENT TYPE
STEP 3
STEP 3
AIR CLEANER COVER
AIR CLEANER
COVER
URETHAN FOAM
PAPER
ELEMENT
URETHANE FOAM
M6 x 20
FLANGE BOLT : 1 pc.
AIR CLEANER COVER
STEP 2
BREATHER
PIPE
Fig. 5-3
- 16 -
M6 FLANGE
NUT : 2 pcs.
Step
Parts to remove
Remarks and procedures
Fasteners
Stop switch
Disconnect the wire and remove the stop
switch from the blower housing.
Recoil starter
Remove the recoil starter from the blower
housing.
10 mm box spanner
M6 × 8mm : 4 pcs.
Blower housing
Baffle 2 (head)
Baffle 3
(1)Remove the blower housing from the
crankcase.
(2)Remove the baffle 2 (head) and baffle 3.
10 mm box spanner
M6 × 12mm : 4 pcs.
10 mm box spanner or
spanner
M6 × 12mm : 2 pcs.
(Baffle 2 (head))
M5 tapping bolt : 2 pcs.
(Baffle 3)
4
5
6
M6 x 8 BOLT : 4 pcs.
M6 x 12 BOLT : 4 pcs.
STEP 4
STEP 5
M4 TAPPING SCREW : 2 pcs.
STOP SWITCH
RECOIL STARTER
BLOWER HOUSING
STEP 6
BAFFLE 2 (HEAD)
BAFFLE 3
(EX21 ONLY)
M6 x 12 BOLT : 1 pc.
M5 TAPPING BOLT : 2 pcs.
STEP 6
Fig. 5-4
- 17 -
Step
Parts to remove
Fuel tank
Fasteners
(1) Drain fuel from the carburetor drain.
(2) Remove the fuel tank mounting nuts
and bolts from the crankcase.
(3) Disconnect the fuel pipe from the carburetor.
(See Fig. 5-6)
(4) Remove the fuel tank from the crankcase.
7
8
Remarks and procedures
Muffler and Muffler cover (1) Remove the muffler cover from the
muffler.
(2) Remove the muffler from the cylinder
head. Take care not to lose the gasket.
※Take care not to cut your hand with the
muffler gasket.
※Seal the exhaust port with adhesive
tape or plug it with cloth to prevent nuts
and other objects from falling inside.
STEP 7
10 (12) mm spanner or box
wrench
M6 nut : 2 pcs.
(Models EX13, 17 and 21)
M8 nut : 2 pcs. (Model EX 27)
M6 × 25mm : 1 pc.
(Models EX 13, 17 and 21)
M8 × 25mm : 2 pcs.
(Model EX27)
12mm box spanner
10mm box spanner or
spanner
M6 tapping bolt : 2 pcs.
M6 × 8mm : 1 pc.
M8 nut : 2 pcs.
M8 × 12mm : 1 pc.
M6 x 10
TAPPING BOLT : 2 pcs.
FUEL TANK
STEP 8
M6 x 8
FLANGE BOLT : 1 pc.
M8 NUT : 2 pcs.
M6 NUT : 2 pcs.
(EX13,17,21)
M8 NUT : 2 pcs.
(EX27)
A
M6 x 25 BOLT : 1 pc.
(EX13, 17, 21)
M8 x 25 BOLT : 2 pcs.
(EX27)
MUFFLER
M8 x 12
BOLT : 1 pc.
FUEL PIPE
A
GASKET
(It has two faces)
FUEL DRAIN
Seal the exhaust port with
adhesive tape or plug it with cloth.
Fig.5-5
Fig.5-6
- 18 -
Step
Parts to remove
Governor system
(1) Loosen the bolt and remove the governor
lever from the governor shaft. There is no
need to remove the bolt.
(2) Remove the governor spring.
(3) Remove the governor rod and the rod
spring from the carburetor.
Carburetor, Insulator
Remove the carburetor from the cylinder head.
Remove the insulator.
9
10
11
Fasteners
Remarks and procedures
10 mm box spanner or
spanner
M6 × 30mm : 1 pc.
Speed control lever and Remove the speed control lever and bracket
Bracket
from the cylinder head.
10 mm box spanner
M6 × 12mm : 2 pcs.
GOVERNOR ROD
and ROD SPRING
STEP 9
GOVERNOR SPRING
GOVERNOR LEVER
M6 x 12 BOLT : 2 pcs.
STEP 11
GOVERNOR SHAFT
SPEED CONTROL LEVER
and BRACKET
GASKET
GASKET
CARBURETOR
INSULATOR
STEP 10
Fig.5-7
- 19 -
Step
12
Parts to remove
Fasteners
Ignition coil
Remove the spark plug cap from the spark plug and
remove the ignition coil from the crankcase.
10 mm box spanner
M6 × 25mm : 2 pcs.
Starting pulley
Remove the starting pulley from the flywheel.
Fit a box wrench or a socket wrench on the flywheel nut
and loosen the nut by knocking the wrench sharply with a
hammer. (See Fig. 5-10)
NOTE:
1) Do not insert a screwdriver or other object between the
flywheel blades, otherwise the risk of damaging the
blades might be occured.
2) Knock the wrench with a hammer in a counter
clockwise direction.
3) The fan of the Model EX21 engine is made of
synthetic resin. Take the utmost care when handling it.
19 (24) mm box spanner or
socket wrench M14 nut
(Models EX13, 17 and 21)
M18 nut (Model EX27)
Flywheel
Flywheel puller
Remove the flywheel from the crankshaft. Leave the nut
temporarily to prevent the flywheel from dropping out. Fit
the flywheel puller as shown in Figure 5-11 and remove
the flywheel from the crankshaft by rotating the bolt at the
center in a clockwise direction.
(Knock the center bolt with a hammer sometimes)
13
14
Remarks and procedues
ATTACH NUT
TEMPORARILY
FLYWHEEL PULLER
Fig. 5-10
Fig. 5-11
STEP 14
STARTING
PULLEY
M14 NUT : 1 pc. (EX13,17,21)
M18 NUT : 1 pc. (EX27)
FLYWHEEL
STEP 13
M6 x 25 BOLT and
WASHER : 2 pcs.
STEP 12
GROMMET
(EX13,17,21 only)
Fig. 5-9
- 20 -
Step
15
Parts to remove
Electric starter (option)
Control box,
Diode rectifier,
Magnetic switch
Remarks and procedures
Fasteners
(1) Disconnect the grounding cable from battery.
(2) Disconnect the wire leading from the key
switch“ST” terminal to the magnetic switch.
(3) Disconnect the wire that connects the
positive terminal of the battery to the
magnetic switch.
(4) Remove the electric starter.
12 mm box spanner
M8 nuts
10 mm box spanner
12 mm box spanner
M6 NUT : 1 pc. (EX17,21)
M8 NUT : 1 pc. (EX27)
ELECTRIC STARTER
(option)
EX27
M8 x 28 BOLT : 2 pcs.
EX17, 21
UPPER SIDE
M6 x 30 FLANGE BOLT : 1 pc.
DOWN SIDE
M6 x 20 FLANGE BOLT : 1 pc.
STEP 15
Fig. 5-8
- 21 -
Step
Parts to remove
Remarks and procedures
Fasteners
Baffle 1 (case)
Remove the baffle 1 (case)
M6 × 12mm : 1 pc.
(Models EX13, 17 and 21)
M8 × 12mm : 1 pc.
(Model EX27)
Charge coil (option)
Remove the charge coil.
(For EX27, remove the wire clamp together)
box spanner
M6 × 20mm : 2 pcs.
+ screwdriver
Spark plug
Remove the spark plug from the cylinder head. 21 mm plug wrench
16
17
18
BAFFLE 1 (CASE)
M6 x 12 FLANGE BOLT : 1 pc. (EX13, 17, 21)
M8 x 12 FLANGE BOLT : 1 pc. (EX27)
For the model without electric starter.
A
STEP 16
STEP 17
CHARGE COIL
SPACER
SPACER
15W
40W
EX17 15W
40W
200W
EX21 15W
40W
200W
EX27 15W
40W
200W
EX13
STEP 18
SPARK PLUG
NA
NA
NA
NA
NA
CLAMP
CHARGE COIL
Fig.5-12
- 22 -
VIEW A (EX27 only)
BOLT
M6 x 40L
M6 x 35L
M6 x 35L
M6 x 40L
M6 x 25L
M6 x 35L
M6 x 40L
M6 x 25L
M6 x 20L
M6 x 30L
M6 x 25L
Step
Parts to remove
Remarks and procedures
Fasteners
Rocker cover
(1) Remove the rocker cover from the
cylinder head.
(2) Remove the gasket (rocker cover).
Rocker arm
Remove the pin (rocker arm) and the rocker
arm from the cylinder head at the compression
top dead center. (See Fig. 5-14b)
19
20
ROCKER ARM
(EXHAUST VALVE SIDE)
PIN
(ROCKER ARM)
10 mm box spanner
M6 × 12mm : 4 pcs.
The position of compression top dead center
Punch marks
ROCKER ARM (INTAKE VALVE SIDE)
Fig. 5-14a
Fig. 5-14b
ROCKER ARM
(EXHAUST
VALVE SIDE)
STEP 20
ROCKER ARM
(INTAKE VALVE SIDE)
PIN
(ROCKER ARM)
CLOSE-UP A
GASKET (ROCKER COVER)
A
STEP 19
ROCKER COVER
Fig. 5-13
- 23 -
M6 x 12 BOLT : 4 pcs.
Step
Parts to remove
Main bearing cover
21
Remarks and procedures
(1) Remove the flange bolts of main bearing
cover from the crankcase.
Remove the main bearing cover while
tapping gently around the cover using
a plastic hammer or similar tool.
(See Fig. 5-16)
Be careful not to damage the oil gauge
or oil seal or not to lose the pipe knocks.
Fig. 5-16
M8 x 35mm : 6 pcs.
(MODELS EX13,
17 AND 21)
M8 x 35mm : 7 pcs.
(MODEL EX27)
STEP 21
PIPE KNOCK
MAIN BEARING COVER
Fig. 5-15
- 24 -
Fasteners
12 mm box spanner
M8 × 35mm : 6 pcs.
(Models EX13, 17 and 21)
M8 × 35mm : 7 pcs.
(Model EX27)
Step
Parts to remove
Remarks and procedures
Tensioner, Camshaft
22
(1) Remove the tensioner. (See Fig. 5-18a)
※Do not lose the pin (tensioner).
(2) Remove the retaining bolt of pin (camshaft)
from the cylinder head. (See Fig. 5-18b)
(3) Remove the pin (camshaft), taking care not
to scratch the O-ring.
(4) Remove the chain from the camshaft
sprocket and then take out the camshaft.
(See Fig. 5-19)
(5) Remove the chain from the crankshaft.
Fasteners
M10 box spanner or spanner
M6 × 12mm : 1 pc.
PIN (CAMSHAFT)
M6 x 12 BOLT : 1 pc.
Bolt used to prevent the
pin (camshaft) from coming out
PIN (TENSIONER)
Fig.5-18a
Fig.5-18b
CHAIN
CAMSHAFT
Fig.5-19
CHAIN
CAMSHAFT
STEP 22
SPRING
(TENSIONER)
M6 x 12 BOLT : 1 pc.
Bolt used to prevent the
pin (camshaft) from coming out
PIN (CAMSHAFT)
TENSIONER
PIN (TENSIONER)
STEP 22
Fig. 5-17
- 25 -
CHAIN
Step
Parts to remove
Fasteners
Cylinder head,
Chain guide
(1) Remove the cylinder head from the
12 mm box spanner
crankcase.
M8 × 68mm : 4 pcs.
(2) Remove the cylinder head gasket from the M8 × 35mm : 1 pc.
cylinder head. Take care not to lose the
pipe knocks.
(3) Remove the chain guide from the top side
of the crankcase.
(If the chain guide is removed from the inner
side of the crankcase, it might be damaged.)
Intake and exhaust
valves
(1) Remove the collet valve from the
spring retainer. (See Fig. 5-21)
(2) Remove the intake valve and the exhaust
valve.
23
24
Remarks and procedures
Fig.5-21
COLLET VALVE
SPRING RETAINER
VALVE SPRING
PIPE KNOCK
GASKET
Push
STEP 23
INTAKE
VALVE
M8 x 68 BOLT : 4 pcs.
VALVE SPRING
EXHAUST
VALVE
STEP 24
COLLET VALVE
STEM SEAL
CHAINGUIDE
CYLINDER HEAD
M8 x 35 BOLT : 1 pc.
(This bolt is same as the
main bearing cover bolt).
Fig.5-20
- 26 -
SPRING RETAINER
Step
Parts to remove
Connecting rod and
piston
(1) Scrape off any carbon from the cylinder
and the piston head, then remove the
connecting rod bolt.
(2) Remove the connecting rod cap.
(3) Rotate the crankshaft until the piston
comes to its top position. Push the
connecting rod and remove the piston
from the upper part of the cylinder.
Piston and piston rings
(1) Remove the piston clips (2 pcs.). Take
out the piston pin and then remove the
piston from the connecting rod small end,
taking care not to damage the connecting rod
small end.
(2) Remove the piston rings from the piston
by spreading them at the gap.
Take special care not to damage the rings
when doing this.
25
26
Remarks and procedures
Fasteners
10 mm box spanner
M6 × 33mm : 2 pcs.
(Models EX13, 17 and 21)
M7 × 40mm : 2 pcs.
(Model EX27)
STEP 26
STEP 25
PISTON RING
CONNECTING ROD CAP
CONNECTING ROD
CLIP
PISTON
PISTON PIN
CLIP
M6 x 33 (EX13, 17, 21)
M7 x 40 (EX27)
CONNECTING ROD BOLT : 2 pcs.
Fig.5-22
- 27 -
Step
Parts to remove
Remarks and procedures
Fasteners
Crankshaft
(1) Remove the woodruff key (for the flywheel
magneto).
(2) Remove the crankshaft from the crankcase
by tapping its magneto side end with a plastic Plastic hammer
hammer, taking care not to damage the oil
seal. (See Fig. 5-24)
Oil sensor (option)
(1) Remove the clamp. (See Fig. 5-25)
(2) Remove the oil sensor from the crankcase.
27
28
M6 × 12mm : 1 pc.
M6 × 16mm : 2 pcs.
CLAMP
OIL SENSOR
Fig.5-24
Fig.5-25
M6 x 10 TAPPING
BOLT : 1 pc. (EX27 only)
CLAMP
SHIELD PLATE
(For charge coil only)
CRANKCASE
M6 x 16
BOLT : 2 pcs.
WOODRUFF KEY
OIL
SENSOR
STEP 28
STEP 27
CRANKSHAFT
Fig.5-23
- 28 -
5-4 REASSEMBLY PROCEDURE
5-4-1 NOTES ON REASSEMBLY
(1) Clean the each parts carefully, taking special care with the piston, cylinder, crankshaft, connecting rod and
bearings.
(2) Scrape off any carbon deposits on the cylinder head and the piston head. Be particularly careful when
removing carbon from the piston ring grooves.
(3) Inspect the oil seals for any damage to the lip. Replace them if damaged. Apply oil to the lip before reassembly.
(4) Replace all the gaskets with new ones.
(5) Replace the keys, pins, bolts and nuts with new ones, if necessary.
(6) Tighten nuts and bolts to the specified torque settings.
(7) When reassembling the engine, apply oil to all moving parts.
(8) Check clearances and end plays and adjust, if necessary.
(9) When mounting any major part during reassembly of the engine, rotate it with your hand to check for any
jamming or abnormal noise.
5-4-2 ASSEMBLY STEPS AND PRECAUTIONS
(1) OIL SENSOR
(a) Mount the oil sensor and fix the wire with the clamp.
(b) Mount the shield plate only for charge coil type.
Tightening torque
10.0 N・m
(100 kgf・cm)
OIL SENSOR
(7.2 ft・lb.)
M6 x 16
BOLT : 2pcs.
(c) Mount the control unit. Fix the earth wire of the
CLAMP
control unit at the same time.
SHIELD PLATE(OS)
(See Fig. 5-49a on page 38).
M6 x 12 BOLT : 1pc.
Fig.5-29
(2) CRANKSHAFT
CRANKSHAFT
(a) Wrap the key-way portion of the crankshaft with
polyvinyl tape and insert the crankshaft into the
crankcase, taking care not to damage the oil seal lip.
(b) Insert the woodruff key (for the flywheel magneto).
NOTE: Do not insert the woodruff key before inserting
the crankshaft into the crankcase.
POLYVINYL TAPE
Fig.5-30
- 29 -
(3) PISTON AND PISTON RINGS
OPEN ENDS OF PISTON RING
Install each piston ring in the correct groove of
the piston by widening it enough to slide it over
the piston.
NOTE: Be careful not to twist the rings too much,
as they may be damaged. Install the oil
ring first, followed by the second ring and
then the top ring.
When installing the second ring, make
sure that the ‘N’ mark is face up.
(See Fig. 5-33)
Fig.5-31
1
1
BARREL
(EX13/27)
TOP
RING
TAPER
(EX17/21)
2
3
2
3
SECOND
RING
OIL
RING
TAPER
CUTTER RING
WITH COIL
EXPANDER
THREE-PIECE
CONSTRUCTION
Fig.5-32
MARK "R"
MARK "N"
EX13
EX17, EX21, EX27
Fig.5-33
- 30 -
(4) PISTON AND CONNECTING ROD
The piston is attached to the connecting rod by
the piston pin.
When assembling the piston and connecting rod,
make sure to align the mark on the piston head with
MAG
the ‘MAG’ mark on the connecting rod.
NOTE 1: Before assembling the connecting rod,
When assembling the
piston and connecting
rod, make sure to align
the mark on the piston
head with the ‘MAG’ mark
on the connecting rod.
apply oil to its small end.
NOTE 2: Be sure to insert the clips in the two ends
of the piston pin and check the clips for
any play.
Fig. 5-34
(5) CONNECTING ROD
PISTON RING GUIDE
(a) Install the piston and connecting rod assembly into
CONNECTING ROD
the cylinder by holding the piston rings with the
ring guide, with the ‘MAG’ mark on the connecting
rod on the flywheel side. (If you do not have a ring
guide, hold the piston rings with the fingers and
tap the upper part of the piston with a piece of
G
MA
wood.)
NOTE 1: Apply oil to the piston rings, the large end
of the connecting rod and cylinder before
"MAG" MARK
installing the connecting rod into the
cylinder.
FLYWHEEL SIDE
NOTE 2: The piston ring gaps should be positioned
Fig.5-35
around the piston at 90-degree intervals.
(See Fig. 5-36)
SECOND RING
OIL RING
TOP RING
Fig.5-36
- 31 -
(b) Rotate the crankshaft down to the bottom dead center
and lightly tap the piston head until the large end of
the connecting rod touches the crank pin.
(c) To mount the connecting rod, line up the matching
marks and fit the clinch portions firmly together.
Tightening torque
EX13,17,21
EX27
13.0 - 15.0 N・m
(130 - 150 kgf・cm)
(9.4 - 10.8 ft・lb.)
17.0 - 20.0 N・m
(170 - 200 kgf・cm)
(12.3 - 14.5 ft・lb.)
ALIGNMENT
MARKS
ALIGNMENT
MARKS
(d) Check for free movement of the connecting rod by
Fig. 5-37
turning the crankshaft slowly.
(6) INTAKE AND EXHAUST VALVES
Take the following points into account when
mounting the intake and exhaust valves on the
cylinder head.
NOTE 1: Replace the valve with a new one if it shows
signs of wear. (Refer to the “STANDARD
REPAIR TABLES” on page 78 and 79.)
NOTE 2: Carefully scrape off any carbon deposits
on the combustion chamber. Apply oil to
the valve stems before mounting the intake
and exhaust valves. Insert the valves in the
Fig. 5-38a
cylinder head and place it on a level
COLLET VALVE
workbench. Next, mount the valve springs,
SPRING RETAINER
the spring retainers and collet valves.
VALVE SPRING
(Mount the stem seal on the intake valve
CYLINDER HEAD
guide.)
INTAKE VALVE
STEM SEAL
EXHAUST VALVE
COLLET VALVE
VALVE SPRING
SPRING RETAINER
Fig.5-38b
- 32 -
(7) CHAIN GUIDE
CHAIN GUIDE
Mount the chain guide to the crankcase.
Model EX21
mounting position
Models EX13, 17 and
27 mounting positions
Fig. 5-39b
Fig. 5-39a
(8) CYLINDER HEAD
Inspect and repair any scratches on mounting surface and replace head gasket to new one before installing.
Tightening Torque
1st step
Cylinder head bolts
1
5
M8 × 68mm
flange bolt : 4 pcs.
3
2nd step
1
4
3
2
17.0 - 19.0 N・m
(170 - 190 kgf・cm)
(12.3 - 13.7 ft・lb.)
Remarks
4
2
25.0 - 27.0 N・m
(250 - 270 kgf・cm)
(18.1 -19.5 ft・lb.)
Re-use
28.0 - 30.0 N・m
(280 - 300 kgf・cm)
(20.3 - 21.7 ft・lb.)
When replace to new cylinder
head and flange bolts
--------
--------
M8 × 35mm
flange bolt : 1 pc.
Tighten the cylinder head bolts in diagonal order.
(1) Re-use (Oil the screw thread)
Tighten all bolts (5pcs) by 18 ± 1 N・m primary,
and then tighten longer ones (M8 × 68mm flange
bolt: 4pcs) by 26 ± 1 N・m.
(2) When replace to new cylinder head and flange
bolts (Oil the screw thread)
Tighten all bolts (5pcs) by 18 ± 1 N・m primary,
and then tighten longer ones (M8 × 68mm flange
bolt: 4pcs) by 29 ± 1 N・m.
●
PIPE KNOCK
M8 x 68 BOLT : 4 pcs.
GASKET
●
PIPE
KNOCK
CYLINDER HEAD
M8 x 35 BOLT : 1 pc.
Fig. 5-40
- 33 -
(9) SETTING THE TIMING CHAIN
(a) Align the timing mark on the crankshaft sprocket with the mark plate of the timing chain.
(b) Align the timing mark on the crankshaft sprocket with the mark plate of the opposite end of the timing chain.
Model
Number of oval steel link
EX13
EX17
EX21
EX27
86
88
92
100
CHAIN GUIDE FITTING POSITION
Model EX13
MARK PLATE
The mark plate does
not have a camshaft
side or crankshaft
sprocket side.
The position of
top dead center
TIMING MARK
ROLL PIN
TIMING MARK
CAMSHAFT SPROCKET
MARK PLATE
Model EX17, 27
CRANKSHAFT SPROCKET
CHAIN GUIDE FITTING POSITION
MARK PLATE
The mark plate does
not have a camshaft
side or crankshaft
sprocket side.
TIMING MARK
ROLL PIN
TIMING MARK
MARK PLATE
CAMSHAFT SPROCKET
CRANKSHAFT SPROCKET
CHAIN GUIDE FITTING POSITION
Model EX21
MARK PLATE
The mark plate does
not have a camshaft
side or crankshaft
sprocket side.
TIMING MARK
ROLL PIN
TIMING MARK
MARK PLATE
CAMSHAFT SPROCKET
CRANKSHAFT SPROCKET
Fig. 5-41a
- 34 -
(10) MOUNTING THE CAMSHAFT ON THE CYLINDER HEAD
Mount the camshaft on the cylinder head by inserting the pin (camshaft) through the head.
Fix the bolt to prevent the pin (camshaft) from coming out.
PIN (CAMSHAFT)
CHAIN
M6 x 12 BOLT : 1 pc.
Bolt used to prevent the
pin (camshaft) from coming out
CAMSHAFT
CHAIN
CAMSHAFT
CHAIN
SPRING
(TENSIONER)
M6 x 12 BOLT : 1 pc.
Bolt used to prevent the
pin (camshaft) from coming out
PIN(CAMSHAFT)
TENSIONER
PIN(TENSIONER)
Fig. 5-41b
(11) MOUNTING THE TENSIONER
PIN
(TENSIONER)
SPRING
(TENSIONER)
PIN (TENSIONER)
TENSIONER
Fig. 5-42a
Fig. 5-42b
- 35 -
(12) BALANCER SHAFT (OPTION)
TIMING MARK
(for EX27 only)
Mount the balancer shaft on the crankcase, align
BALANCER GEAR
the timing marks on the balancer gear and the
crankshaft gear.
NOTE: Incorrect alignment of the timing marks
can result in malfunction of the engine,
leading to damage due to interference of
CRANKSHAFT GEAR
the parts.
Fig. 5-43
(13) MAIN BEARING COVER
Apply oil to the bearing and the oil seal lip when mounting the main bearing cover. Also apply sealant
(Three Bond “1215”) to the surface of the crankcase. To avoid damaging the oil seal lip, wrap the crankshaft
key-way portion with polyvinyl tape before mounting the main bearing cover.
NOTE: Be careful that the lever portion of governor shaft does not face the main bearing cover.
Tightening torque
17.0 - 18.0 N・m
(170 - 180 kgf・cm)
(12.3 - 13.0 ft・lb.)
GOVERNOR SHAFT
CRANKSHAFT
M8 x 35 BOLT : 6 pcs.
(EX13, 17, 21)
M8 x 35 BOLT : 7 pcs.
(EX27)
SEALANT
(Three bond "1215")
MAIN BEARING COVER
Fig. 5-44
- 36 -
(14) Pass the pin (rocker arm) through the rocker arm
ROCKER ARM
(EXHAUST VALVE SIDE)
PIN
(ROCKER ARM)
and mount them on the cylinder head.
NOTE 1: Conduct this job at the compression top
dead center.
(The position of two punch marks on cam
sprocket is in parallel with the cylinder
Punch
marks
head surface at a time.)
NOTE 2: Make sure that the piston is at the
The position of compression
top dead center
compression top dead center by checking
ROCKER ARM
(INTAKE VALVE SIDE)
Fig. 5-45
mutual position between the flywheel and
the ignition coil or by checking that the
EX13, 17, 21
key way is at the top.
(See each Fig.5-46)
The position of
top dead center
(15) VALVE CLEARANCE ADJUSTMENT
EX27
Temporarily fit the flywheel.
Rotate the crankshaft up to the compression top
dead center and insert the thickness gauge
between the valve and the adjusting screw of
The position of
top dead center
rocker arm to measure the clearance.
[Adjustment method]
Loosen the nut on the adjustment screw and turn
the screw to adjust the valve clearance. When
the valve clearance is correct, tighten the nut.
The key way
is at the top
Valve clearance (when the engine is cold)
Intake valve side
Exhaust valve side
Tightening
torque
0.12 +0.03
mm
0
(0.0047 +0.0012
in.)
0
Fig. 5-46
THICKNESS GAUGE
NUT
ADJUSTMENT
SCREW
ROCKER ARM
(EXHAUST
VALVE SIDE)
5.0 - 7.0 N・m
(50 - 70 kgf・cm)
(3.6 - 5.1 ft・lb.)
NOTE: After adjusting the valve clearances, rotate
the crankshaft and check again that the
intake and exhaust valve clearance are
correct.
ROCKER ARM
(INTAKE VALVE SIDE)
Fig. 5-47
- 37 -
(16) ROCKER COVER
SPARK PLUG
Replace the gasket with a new one, and mount
the rocker cover.
M6 ✕ 12mm flange bolt : 4 pcs.
Tightening torque
5.0 - 7.0 N・m
(50 - 70 kgf・cm)
(3.6 - 5.1 ft・lb.)
GASKET
(ROCKER COVER)
(17) SPARK PLUG
Remove any carbon deposits from the spark plug
and inspect the electrode for damage before
mounting. Replace with a new one, if necessary.
Tightening torque
0.6 mm - 0.7 mm
(18) BAFFLE 1 (CASE)
Align the top and bottom of the baffle 1 (case)
with the crankcase and mount it with the bolts.
[Model without electric starter]
M6 ✕ 12 mm bolt : 1 pc.
(Models EX13, 17 and 21)
New spark plug
Re-tightening torque
12.0 - 15.0 N・m
(120 - 150 kgf・cm)
(8.7 - 10.8 ft・lb.)
23.0 - 27.0 N・m
(230 - 270 kgf・cm)
(16.6 - 19.5 ft・lb.)
[Model with electric starter]
Mount the electric starter and the charging coil,
referring to the illustrations of disassembly.
Tightening torque
M8 ✕ 12 mm bolt : 1 pc. (Model EX27)
BAFFLE 1 (CASE)
M6 x 12
BOLT : 4 pcs.
Fig. 5-48
Spark plug: NGK BR-6HS
or CHAMPION RL86C
Electrode gap
ROCKER
COVER
UPPER
EX13, 17, 21
EX27
4.0 N・m
(40 kgf・cm)
(2.9 ft・lb.)
12.0 N・m
(120 kgf・cm)
(8.7 ft・lb.)
M6 x 12 FLANGE BOLT : 1 pc.
(EX13, 17, 21)
M8 x 12 FLANGE BOLT : 1 pc.
(EX27)
EX13, 17, 21
TO IGNITION COIL
LOWER
BAFFLE 1
(CASE)
OIL SENSOR
UNIT
HOOK
TO OIL SENSOR
Fig. 5-49b
Fig. 5-49a
- 38 -
(19) FLYWHEEL AND STARTING PULLEY
FLYWHEEL
NOTE: When mounting the flywheel, be sure to
wipe off any oil on the tapered portion of
the crankshaft and flywheel.
Mount the flywheel on the crankshaft. (Tighten
the flywheel together with the starting pulley.)
STARTING PULLEY
Tightening torque
Align the 2 bosses of starting pulley with the depression of flywheel.
59.0 - 64.0 N・m
(590 - 640 kgf・cm)
(42.7 - 46.3 ft・lb.)
Fig. 5-50
M14 nut : 1 pc. (EX13, 17, 21)
M18 nut : 1 pc. (EX27)
Fig. 5-51
THICKNESS
GAUGE
(20) IGNITION COIL
When mounting the ignition coil, insert a
thickness gauge between the ignition coil and
the flywheel to check the air gap.
Air gap
0.3 - 0.5 mm
Tightening torque
IGNITION COIL
7.0 - 9.0 N・m
(70 - 90 kgf・cm)
(5.1 - 6.5 ft・lb.)
Fig. 5-52
M6 ✕ 25 bolt and washer : 2pcs.
To STOP
SWITCH
Fig. 5-53
- 39 -
(21) SPEED CONTROL LEVER, BRACKET AND BAFFLE
Mount the speed control lever and bracket, baffle 2 (head) and baffle 3 on the crankcase.
NOTE : The baffle 3 is used for Model EX21 only.
(22) CARBURETOR
(a) Replace the gasket of insulator with a new one and mount the insulator on the cylinder head intake
side.
(b) Mount the carburetor.
M6 x 12 BOLT : 2 pcs.
SPEED CONTROL LEVER
and BRACKET
CARBURATOR
INSULATOR
GASKET
GASKET
BAFFLE 2 (HEAD)
M6 x 12 BOLT
: 1 pce.
BAFFLE 3
(EX21 ONLY)
A
M5 TAPPING BOLT : 2 pcs.
Detail A
Fig. 5-54
- 40 -
(23) GOVERNOR LEVER
(a) Pass the governor rod through the rod spring, then connect to the throttle lever of the carburetor.
(b) Attach the governor rod and rod spring to the governor lever, then mount the governor lever on the governor
shaft. Do not adjust the bolt on the governor lever yet.
(c) Connect the governor lever and the speed control lever with the governor spring.
NOTE : See page 42 for details on the adjustment method after mounting air cleaner base.
Variation of the governor spring
The dimensions of the governor spring are different each other according to the Hz.
The governor spring for the standard engine is same as that for the engine to be connected to the 60Hz generator.
Discrimination according to the dimensions:
EX13, 17 / 50Hz
10
EX21, 27 / 50Hz
20
Color : Gold
15
15
(Speed con. side)
Color : Gold (Governor lever side)
EX13, 17, 21, 27 / 60Hz (STD)
26
15
Color : Silver
GOVERNOR ROD
and ROD SPRING
GOVERNOR
LEVER
GOVERNOR SPRING
Long
length side
Short
length side
SPEED CONTROL LEVER
and BRACKET
Fig. 5-55
- 41 -
(24) AIR CLEANER BASE
M6 x 20
FLANGE BOLT : 1 pc.
Insert the breather pipe into the rocker cover
AIR CLEANER BASE
and then mount the air cleaner base.
M6 flange nut : 2 pcs.
M6 x 20 mm flange bolt : 1 pc.
Tightening torque
6.0 - 8.0 N・m
(60 - 80 kgf・cm)
(4.3 - 5.8 ft・lb.)
BREATHER
PIPE
M6 FLANGE
NUT : 2 pcs.
Fig. 5-57
■
Governor system adjustment method
The governor unit is a centrifugal flyweight type and is installed on the governor gear.
Since it automatically adjusts the throttle valve of the carburetor by means of a link mechanism, it is possible to
maintain a constant engine speed, even with load variations.
(1) Turn the speed control lever to the full speed position, making sure that the carburetor throttle valve is fully
open.
(2) Hold the top of the governor shaft with the plier and turning it clockwise as far as it will go. Tighten the bolt on
the governor lever.
GOVERNOR
LEVER
GOVERNOR ROD
and ROD SPRING
Tightening torque
8.0 - 10.0 N・m
(80 - 100 kgf・cm)
(5.8 - 7.2 ft・lb.)
GOVERNOR
SPRING
GOVERNOR
SHAFT
Fig. 5-58
- 42 -
(25) MUFFLER
(1) Mount the muffler and the gasket on the cylinder head.
M6 x 10
TAPPING BOLT : 2 pcs.
GASKET
(Attention to the wrong side and right side)
MUFFLER SIDE
(RIGHT SIDE)
M6 x 8
FRANGE BOLT : 1 pc.
M8 NUT : 2 pcs.
CYLINDER SIDE
(WRONG SIDE)
MUFFLER
Take utmost care not to cut your
hand with the muffler gasket
M8 ✕12 mm bolt : 1 pc.
M8 x 12 BOLT : 1 pc.
M8 nut : 2 pcs.
Tightening torque
GASKET
(Attention to the wrong
side and right side)
18.0 - 22.0 N・m
(180 - 220 kgf・cm)
(13.0 - 15.9 ft・lb.)
(2) Mount the muffler cover on the muffler.
M6 ✕ 8 mm flange bolt : 1 pc.
M6 ✕ 10 mm tapping bolt : 2 pcs.
NOTE : Be sure to remove any tape or cloth used
to cover the exhaust port when the engine
was disassembled.
Fig. 5-59a
(26) FUEL TANK
(1) Mount the fuel strainer to the fuel tank.
FUEL
STRAINER
Tightening torque for fuel strainer
FUEL PIPE
3.0 - 4.0 N・m
(30 - 40 kgf・cm)
(2.2 - 2.9 ft・lb.)
(2) Connect the fuel pipe and fix it with a clamp.
Model
EX13
EX17
EX21
M6 NUT
: 2pcs.
HOSE
CLAMP
M6 x 25 BOLT : 1pc.
(EX13, 17, 25)
M8 x 25 BOLT : 2pcs.
(EX27)
EX27
Fuel pipe length
145(5.7) 150(5.9) 155(6.1) 195(7.7)
mm(in.)
NOTE : Make sure the fuel pipe is located on the boss,
as shown in the illustration, in order to prevent
the pipe from attaching to the flywheel.
In case the pipe is routed improperly, the pipe might
be hit by the flywheel and will be damaged.
- 43 -
Fig. 5-59b
(3) Mount the fuel tank on the crankcase.
FUEL PIPE
M6 nut : 2 pcs.
M6 ✕ 25 mm bolt : 1 pc. (Models EX13, 17 and 21)
M8 ✕ 25 mm bolt : 2 pcs. (Model EX27)
BOSS
Fig. 5-59c
(27) BLOWER HOUSING AND RECOIL STARTER
(1) Mount the ignition coil cord on the crankcase by aligning it with the baffle 1 (case).
(2) Mount the blower housing on the crankcase.
M6 × 12 mm bolt : 4 pcs.
(3) Mount the recoil starter on the blower housing.
M6 × 8 mm bolt : 4 pcs.
M6 x 8 BOLT : 4 pcs.
M6 x 12 BOLT : 4 pcs.
RECOIL STARTER
BLOWER HOUSING
Fig. 5-60
- 44 -
(28) STOP SWITCH
STOP SWITCH
(1) Mount the stop switch on the blower housing.
(2) Refer to the wiring diagram (See page 51 and 52) for
wiring details.
Fig. 5-61
(29) AIR CLEANER
Mount the air cleaner element and cleaner cover.
Type
STD
Fig. 5-62
- 45 -
Dual element
(30) EXTERNAL INSPECTION
Reassembly is completed. Check that the wiring is correct and that there are no loose nuts and bolts or any
other faults visible on the outside of the engine.
(31) FILLING WITH ENGINE OIL
Use the automobile engine oil of API service class SE or higher grade.
The amount of oil depends on the engine model. Refer to the table below.
Model
EX13
Model
EX17
Engine oil volume
Model
EX21
0.6 L
Model
EX27
1.0L
(32) BREAK-IN OPERATION
A new engine or an engine that has been completely overhauled by being fitted with a new piston, rings,
valves and connecting rod should be thoroughly RUN-IN before being put back into service.
Good bearing surfaces and running clearances between the various parts can only be established by operating
the engine under reduced speed and loads for a short period of time.
While the engine is being tested, check for oil leaks.
Make final carburetor adjustment and regulate the engine operating speed.
Step
Model
EX13
Model
EX17
Model
EX21
Model
EX27
Engine
Speed
Time
Step 1
No Load
2500 r.p.m.
10 min.
Step 2
No Load
3000 r.p.m.
10 min.
Step 3
No Load
3600 r.p.m.
10 min.
Step 4
1.5 HP
2 HP
2.5 HP
3.5 HP
3600 r.p.m.
30 min.
Step 5
3 HP
4 HP
5 HP
7 HP
3600 r.p.m.
30 min.
- 46 -
6. ENGINE OIL
Using engine oil of the correct grade and viscosity greatly lengthens engine life and improves performance.
Too much or too little oil can also result in serious problems, including engine seizure.
6-1 CLASSIFICATION BY OIL GRADE
API (American Petroleum Institute)
Classification
SA
SB
SC
SD
SE
SF
SG
SH
SJ
Grades suited for Robin Engine: SE or higher (SG,SH or SJ in recomended)
6-2 CLASSIFICATION BY OIL VISCOSITY
SAE (Society of Automotive Engineers)
5W
10W
Single grade
20W
#20
#30
#40
Multigrade
10W-30
10W-40
Ambient
temperature
Be sure to use automobile engine oil of the viscosity shown in the table above, depending on environmental air
temperature.
When the air temperature falls below –20°
C or rises above 40°
C , be sure to choose engine oil of appropriate
viscosity and grade, according to the prevailing conditions.
※ Care must be taken when using multi-grade engine oil, because the oil consumption rate tends to increase
when the air temperature is high.
6-3 ADDING AND CHANGING ENGINE OIL
○ Engine oil inspection and filling up ............. Every time you use the engine
(add engine oil up to the designated maximum level)
○ Engine oil change ..................................... First time ............ After 20 hours’ use
Thereafter ........... Every 100 hours’ use
- 47 -
7. MAGNETO
7-1 MAGNETO
The Robin Engine uses a T.I.C. type breakerless magneto ignition system.
(1) T.I.C. (TRANSISTOR IGNITER CIRCUIT) has the ignition coil outside the flywheel, which is the standard
specification. A charge coil system is available as an option.
(The flywheel is a specialized piece of equipment.)
As for the lighting coil, the ignition coil is outside the flywheel and a lighting coil is inside.
7-2 INSPECTING THE MAGNETO
If the engine does not start, has difficulty starting, or does not run smoothly, check the magneto for defects
according to the following procedure:
(1) Carefully check the high-tension cable for any damage or short circuiting.
(2) Check the sparking.
① Take the spark plug out of the cylinder head, connect the spark plug with the plug cap and ground it
on the cylinder head or any other metallic part of the engine.
(The gap between the electrodes of the spark plug should be between 0.6 mm and 0.7 mm).
② Rotate the engine by pulling the recoil starter and check the spark plug gap for sparking. If the spark
plug is sparking, check the intensity of the spark.
(Before checking the spark plug, disconnect the primary wire from the connector.)
③ Next, disconnect the spark plug from the plug cap and check the end of the high-tension cable for
sparking.
- 48 -
7-3 IGNITION SYSTEM (EX13 ,17, 21)
7-3-1 TYPE OF IGNITION SYSTEM
Secondary Coil
Primary Coil
I2
I4
Spark Plug
I5
Ignition Coil
Automatic
Advancing
Control
Circuit
Power Transistor
LowSpeed
I3
Ignition
Timing
Control Circuit
I1
Signal Transistor B
Signal Transistor A
Resister
EX13, 17 and EX21 have the T.I.C. (Transister, Igniter, Circuit) pointless ignition system.
As optional parts, these ignition system may be implemented with lamp coil, charge coil and excitor coil.
I6
Fig. 7-1(a)
7-3-2
BASIC THEORY
(B.T.D.C)
23ࠑ
IGNITION TIMING
To ensure the easy startability of the engine, the
step advancing ignition timing system is
incorporated in the ignition coil. This system
enables the engine to have basically two different
ignition timings according to the engine speed.
Following are the explanation how the system works.
ELECTRONIC ADVANCING FLYWHEEL
MAGNETO SYSTEM
STEP ADVANCING
1) At lower speed of the engine
15ࠑ
Rotation of the flywheel induces current I1,
500
1000
2000
3000(r.p.m.)
as this current flows through the base terminal
ENGINE REVOLUTION
of the power transister, it is activated and the
Fig. 7-1(b)
current I2 starts flowing.
As the engine reaches the ignition timing, the ignition timing control circuit for the lower engine speed is
activated and lets the current I3 flow through the base terminal of the power transistor.
This generates the collector current I4 which will bypass the current I1 and abruptly shut off the current I2
because the power transistor is turned off.
This sudden current change generates a big voltage on the secondary side of the ignition coil and which
sparks the spark plug.
2) At the higher engine speed
Rotation of the flywheel generates the current I1 as this current flows through the base terminal of the power
transistor, it is activated and the current I2 starts of flow.
As the engine reaches the ignition timing, the ignition timing control circuit for the higher engine speed is
activated and provides the base current I5 to the power transistor. This current induces the collector current
I6 and will bypass the current I1 to shut down the current I2 abruptly because the power transistor is turned off.
This sudden current change generates a big voltage on the secondary side of the ignition coil and which will
spark the spark plug.
The ignition timing control circuit for the higher engine speed is activated, sooner than the control circuit for
the lower speed and not activated when the engine speed is in a lower range.
- 49 -
7-4 IGNITION SYSTEM (EX27)
IGNITION COIL INTERNAL CIRCUIT
Low Speed Ignition
Timing Control
Circuit
Advancing Control
Circuit
I4
I5
4
7
1
Spark Plug
I3
2
Secondary Coil
Control thyristor
5
3
I2
Primary Coil
I1
Power Transistor
Base Resister
Revolution Sensing
Resister
7-4-1
6
Fig.7-2a
7-4-2
IGNITION TIMING CHARACTERISTIC
LINEAR ADVANCING
35
IGNITION TIMING
B.T.D.C. ( )
30
25
20
15
10
5
0
0
500
1000
1500
2000
2500
3000
3500
4000
ENGINE REVOLUTION (R.P.M.)
Fig.7-2b
7-4-3
BASIC THEORY
(a) Revolution of the flywheel generates electricity on the primary side of the ignition coil (①), and the base
current I1 flows to the power transistor ( ② ). Current I1 turns the power transistor “ON” and the electric
current I2 flows. This is the same situation when the contact breaker is closed in a case of breaker point
type ignition system.
(b) At lower engine revolution, the low speed ignition timing control circuit ( ③ ) operates to run the gate
current I3 to turn the control thyristor ( ⑤ ) “ON”, thus the current I1 bypass the thyristor as current I5.
At this moment, the power transistor (②) turns “OFF” and the current I2 is shut off abruptly resulting
in the high voltage generated in the secondary coil (⑦) which produces sparks at the spark plug.
The ignition timing at lower engine revolution is less advanced as shown in the above chart.
(c) At higher engine revolution (over 2,000rpm), advancing control circuit (④) operates to run the gate current
I4 to turn the control thyristor ( ⑤ ) “ON”, thus the current I1 bypass the thyristor as current I5.
At this moment, the power transistor (②) turns “OFF” and the current I2 is shut off abruptly resulting
in the high voltage generated in the secondary coil (⑦) which produces sparks at the spark plug.
At over 2,000rpm, ignition timing on each engine revolution is controlled by advancing control circuit (④)
that receive electrical information from revolution sensing resister ( ⑥ ).
The advancing of ignition timing from lower to higher engine revolution changes lineally as shown in
the above chart.
- 50 -
8. WIRING DIAGRAM
8-1 MODEL WITHOUT ELECTRIC STARTER (Models EX13, 17, 21 and 27)
Spark plug
Stop switch
Black
Ignition coil
(with built-in transistor)
Flywheel
Fig. 8-1
8-2 MODEL WITH ELECTRIC STARTER (Models EX17 and 21)
Spark plug
Black
Magneto
Ignition coil
Key switch
+M
-M
Charge coil
Diode rectifier
LA306
ST
B
Red
LA106
LA406
Key switch
066-00003-30
-M
OFF
ON
START
+M
B
S
Magnetic switch
Electric starter
Fig. 8-2
- 51 -
Battery
(12V24AH)
8-3 MODEL WITH ELECTRIC STARTER (Model EX27)
Spark plug
Black
Magneto
Ignition coil
Key switch
+M
-M
Charge coil
Diode rectifier
ST
B
LA108
LA408
Red
Battery
(12V24AH)
Key switch
066-00003-30
-M
+M
B
S
OFF
ON
START
Electric starter
Fig. 8-3
8-4 MODEL WITH OIL SENSOR
To LED Lamp
Yellow
Yellow / Red
Oil sensor Orange
Black
Black / White control unit
Body
earth
LA106
Black
Orange Oil
sensor
To stop switch
Spark
plug
※ Oil sensor as option
Fig. 8-4
- 52 -
9. ELECTRIC STARTER
EX 17, 21
9-1 SPECIFICATIONS
129.5
Models EX17, 21
Pinion gear
Model EX27
Voltage
(V)
12
Power
(kW)
0.6
0.6
Weight
(kg)
1.6
3.4
EX 27
PINION GEAR
157.8
Fig. 9-1
9-2 OPERATING PRINCIPLES
The battery is connected to the 6 or 8 mm diameter terminal of the magnetic switch.
The figure below shows the state when the starter is ON.
M
M
S
S
M
M
ELECTRIC STARTER
MAGNETIC
SWITCH
BATTERY
M
KEY SWITCH
Fig. 9-2
There are two energized circuits: the magnetic switch (M) circuit and the starter motor (S) circuit. When the key
switch is ON, the (M) circuit is closed, the current flows in the direction of the arrows, the coil of the magnetic
switch is magnetically excited and the contactor is pulled.
As a result, a low current flows through the (M) circuit and a high starter current flows through the (S) circuit.
This energizes the starter motor and cranks the engine.
◇ Engagement of the pinion gear (EX17,21)
When the starter motor is started, the weight built into the spiral splines located on the shaft moves in the direction
of the axis driven by centrifugal force and pushes out the pinion gear, and the pinion gear engages the ring gear.
- 53 -
9-3 COMPONENT PARTS
(Models EX17 and EX21)
PINION AY
FRONT COVER
MAGNETIC SWITCH
PINION
STOPPER SET
BATTERY
CABLE
THROUGH BOLT (2 pcs.)
O - RING
WASHER
YOKE AY
O - RING
ARMATURE AY
BRUSH
SPRING (BRUSH)
REAR COVER
BRUSH HOLDER
(Model EX27)
MAGNETIC SWITCH
PINION AY
ARMATURE AY
YOKE AY
SPRING (BRUSH)
BRUSH
FRONT COVER
CASE METAL
BRUSH HOLDER
REAR COVER
FRONT METAL
THROUGH BOLT (2 pcs.)
PINION STOPPER SET
Fig. 9-3
- 54 -
10. OIL SENSOR
10-1 SPECIFICATIONS
Type
Float type
(with lead switch incorporated)
Resistance
(at FULL oil level)
100 M ohms or over
Operating
Temperature
-30 to +180 degree Celsius
OIL SENSOR
Fig.10-1
10-2 CONSTRUCTION AND OPERATION
The oil sensor is composed of the float, permanent
magnet incorporated into the float and the oil sensor.
In accordance with the oil level, the float moves up and
down.
When the oil level is upper level, the float moves up.
FLOAT
PERMANENT MAGNET
LEAD SWITCH
Fig.10-2
When the oil level is lower level, the float moves down.
The permanent magnet is close to the lead switch, and
the lead switch is activated by the magnetic force.
MAGNETIC FORCE
Fig.10-3
NOTE : With regards to the wiring diagram,
please refer to the section 8-4 (page52).
- 55 -
11. AUTOMATIC DECOMPRESSION SYSTEM
11-1 FUNCTIONS AND CONSTRUCTION
EX series engines employ an automatic decompression system as a standard feature. This enables easy
starting of the engine, with lighter recoil pull.
The automatic decompression system releases the compression of the engine by lifting up the exhaust valve at
cranking speed. The following is the explanation of the function.
At the end of the compression process, the release lever lifts up the rocker arm (exhaust) which in turn opens
up the exhaust valve slightly to release the compression.
The release lever has a flyweight on its end and another end of the lever is a crescent cam.
When the engine is cranked, the crescent cam projects above the cam profile and lifts up the rocker arm
(exhaust) because the force of the return spring on the weight is larger than the centrifugal force on the weight.
ROCKER ARM
(EXHAUST)
ROCKER ARM
(EXHAUST)
ROCKER ARM
(INTAKE)
RELEASE LEVER
CAM
CRESCENT CAM
CAMSHAFT
RELEASE LEVER
A
Fig. 11-1
DETAIL A
When the cranking speed reaches a specified r.p.m., the crescent cam is retracted under the cam profile
because the centrifugal force applied to the flyweight becomes larger than the force of the return spring on the
weight and thus it is shifted to the position shown in the illustration below.
RELEASE LEVER
ROCKER ARM
(EXHAUST)
ROCKER ARM
(EXHAUST)
ROCKER ARM
(INTAKE)
CAM
CRESCENT CAM
A
CAMSHAFT
RELEASE LEVER
Fig. 11-2
DETAIL A
11-2 INSPECTION
When assembling the release lever, make sure that it works smoothly.
- 56 -
12. CARBURETOR
12-1 SPECIFICATIONS
EX13
EX17
EX21
EX27
A/C Type
STD
DUAL
STD
DUAL
STD
DUAL
STD
DUAL
Main Jet
70.0
68.8
81.3
80.3
86.3
83.8
98.0
96.0
Pilot Jet
40.0
40.0
40.0
40.0
41.3
←
40.0
←
Pilot Screw Turning
1-3/4
←
1-1/4
←
1
←
1-1/2
←
12-2 FUNCTIONS AND CONSTRUCTION
12-2-1 FLOAT SYSTEM
The float chamber is located below the carburetor body. Through the operation of the float and the needle
valve, the float chamber maintains a constant fuel level while the engine is working.
The fuel flows from the tank into the float chamber through the needle valve. When the fuel rises to a
specific level, the float rises. When the buoyancy of the float is balanced with the fuel pressure, the needle
valve shuts off the fuel passage, thereby maintaining the fuel at the predetermined level.
12-2-2 PILOT SYSTEM
The pilot system supplies fuel to the engine during idling and low-speed operation.
Fuel is initially metered by the main jet and then metered once again by the pilot jet. At the pilot jet, the fuel
is mixed with air metered by the pilot air jet and then the fuel/air mixture is fed to the engine through the pilot
outlet and the bypass. During idling, fuel is fed to the engine mainly through the pilot outlet.
12-2-3 MAIN SYSTEM
The main system feeds fuel to the engine at medium and high speed operation.
Fuel is metered by the main jet and flows into the main nozzle. Air metered by the main air jet is mixed with
fuel through the bleed holes of the main nozzle. The fuel/air mist is injected into the Venturi and mixed once
again with air from the air cleaner. This fuel/air mixture is now of optimum concentration and is fed into the
combustion chamber of the engine.
12-2-4 CHOKE SYSTEM
The choke system is for easier start of the engine in cold weather conditions.
When the engine is started with a closed choke, the negative pressure applied to the main nozzle increases.
This causes a larger amount of fuel to be drawn into the carburetor, which in turn makes it easier to start
the engine.
- 57 -
FUEL SYSTEM OUTLINE
FUEL
NEEDLE
VALVE
FLOAT
FLOAT CHAMBER
Fig. 12-1
PILOT OUTLET
PILOT JET
BYPASS
PILOT AIR JET
MAIN NOZZLE
AIR INTAKE PORT
CHOKE VALVE
FLOAT
MAIN AIR JET
MAIN JET
Fig. 12-2
- 58 -
12-3 DISASSEMBLY AND REASSEMBLY
Mechanical failures aside, most carburetor malfunctions occur when the fuel/air ratio of the mixture is not
correct. This is usually caused by clogged jets, air passages and fuel passages, or by variations in the fuel
level.
To get the best possible performance from the carburetor, ensure that the each passages are kept clean so that
air and fuel can flow freely through them.
MODEL EX13, 17, 21
MODEL EX27
21 20 19
18 21 20 13 14
24
18
17
23 22
25
26
22
23
16
27
26
28
25
24
14
1
1
13
12
12
11
2
3
11
3
10
4
4
10
5
5
6
7
6
7
9
9
8
8
Fig. 12-3
- 59 -
The procedures for overhauling the carburetor are described below. (Refer to Fig. 11-3.)
12-3-1 THROTTLE SYSTEM
(1) When the throttle stop screw 26 is removed, the spring 25 can be taken out.
(2) Remove the phillips screw 22 and the throttle valve 23, then take out the throttle shaft 24 .
When removing the throttle valve, take care not to damage the valve edge.
12-3-2 CHOKE SYSTEM
(1) Remove the choke valve ⑭. Then pull out the choke shaft ⑬.
(2) When reassembling the choke shaft, be sure to position the cutout on the choke valve facing the pilot air
jet.
12-3-3 PILOT SYSTEM
(1) Remove the pilot jet ⑱. Use the correct tool so as to avoid damaging the jet.
(2) When reassembling the pilot jet, be sure to firmly tighten it, otherwise fuel may leak, leading to engine
malfunction.
12-3-4 MAIN SYSTEM
(1) Remove the bolt ⑧ and remove the float chamber body ⑤.
(2) Remove the main jet ⑪ from the body ①.
(3) Remove the main nozzle ② from the body ①.
(4) When reassembling the main system, be sure to fasten the main jet and main nozzle firmly to the body,
otherwise the fuel concentration in the fuel/air mixture may become too rich, leading to engine malfunction.
(5) The tightening torque of the bolt ⑧ is 9 N・m (90 kgf・cm / 6.5 ft・lb.). Be sure not to forget to mount the
washer.
12-3-5 FLOAT SYSTEM
(1) Take out the float pin ⑩ and then remove the float ④ and the needle valve ⑫.
※Since the needle valve ⑫ is linked to the float ④, take care when assemble.
※Do not use drill or similar objects for cleaning the jets, as these are likely to damage the orifices, which
in turn can impair fuel flow. Use compressed air to clean the jets.
※The float pin is pressed into the carburetor body. When removing the needle valve and the float, a rod
or a similar tool slimmer than the float pin should be used. Tap the reverse side gently and remove.
- 60 -
13. RECOIL STARTER
13-1 RECOIL STARTER
Tools required: Screwdriver, pliers and protective glasses
NOTE:
Put on the protective glasses prior to start disassembly.
13-1-1 DISASSEMBLY PROCEDURE
(1) Release the reel spring power
-1 Hold the starter knob and pull out the starter
rope.
-2 Pull out the rope fully and align the rope knot in
the reel with the rope guide.
-3 Hold the reel down firmly with both thumbs,
taking care not to allow it to spring back.
(Fig. 12-1)
-4 Remove the knot from the reel, untie the knot
and pull the rope out toward the starter knob.
Fig. 13-1
Note: This procedure requires 2 people.
-5 While controlling the reel with the thumbs, slowly
wind it back as far as it will go.
NOTE:
When the rope is pulled out to its full length, the force stored in the spring reaches its maximum.
Be careful not to drop it or release your grip on it suddenly.
- 61 -
(2) Remove the components. (Fig. 13-2)
-1 Grip the case and loosen the set screw.
SET SCREW
-2 Take out the set screw, the ratchet guide,
RATCHET
GUIDE
the friction spring and the ratchet in that
order.
FRICTION
SPRING
(3) Remove the reel. (Fig. 13-2)
-1 Hold down the reel gently to keep it from
RATCHET
escaping from its case and rotate it slowly
back and forth by quarter turns until it moves
smoothly.
REEL
-2 Lift the reel up little by little and take it out of
the case.
-3 If the spring is about to pop out of the reel,
repeat steps (3)-1 and (3)-2.
STARTER CASE
NOTE:
Fig. 13-2
Since the spring is stored in the reel, make sure
not to drop or shake the reel after removing it.
Place it on a level surface such as a table.
Disassembly is completed.
NOTE:
Put on the protective glasses prior to start reassembly.
13-1-2 REASSEMBLY PROCEDURE
(1) Put the reel back into the case
GREASE
-1 Apply grease to the surface of the case.
(Fig.13-3)
-2 Adjust the position of the inner end of the
spring in the reel. (Fig. 13-4)
-3 Hold the reel in such a way that the inner end
SHAFT HOOK
of the spring hooks onto the shaft hook and
then place the reel carefully back into the case.
-4 Turn the reel gently counterclockwise to
Fig. 13-3
Position where the inner end of the
spring touches to the rib of the bearing.
Fig. 13-4
confirm that the spring is hooked.
- 62 -
(2) Mount the components
-1 Mount the ratchet into the reel. (Fig. 13-5)
THE RATCHET SHOULD
BE IN THE CLOSED POSITION
Fig. 13-5
-2 Mount the ratchet guide assembly, taking care
Set screw
not to move the ratchet. (Fig.13-6)
Ratchet
guide
Friction spring
Ratchet guide sub-assembly
Fig. 13-6
(3) Tighten the set screw
-1 Hold the ratchet guide gently by your hand to
prevent it from rotating, then tighten the set
ROPE HOLE IN REEL
screw.
Tightening torque(M6)
5.5 N・m
(55 kgf・cm)
(4.0 ft・lb.)
A
FR PPR
O OX
M
TH . 20
E 0M
RE M
EL
(4) Tension the reel spring
ROPE GUIDE
-1 Grip the case and turn the reel 6 times
counterclockwise.
-2 Fix the reel so that the rope hole in the reel is
Fig. 13-7
aligned with the rope guide. (Fig. 13-7)
NOTE:
The spring force reaches its maximum value when the reel is wound up. Be careful not to drop
it or release your grip on it suddenly.
- 63 -
(5) Install the rope
NOTE: This procedure requires 2 people.
-1 Pass the rope end through the rope guide and the
Approx. 20mm
rope hole of the reel and pull through approximately
20 cm out of the reel. (Fig. 13-7)
-2 Tie a knot in the rope end . (Fig. 13-8)
-3 Put the rope into the reel, taking care that the
rope end does not stick up. (Fig. 13-9)
-4 Grasp the rope firmly with one hand at
approximately 50 cm from the rope guide and
keep the rope tense, taking care that the rope
Fig. 13-8
is not pulled into the reel.
-5 Release the reel carefully and allow the rope to
be wound back slowly by the force of the spring
until the knob reaches the rope guide.
Assembly is completed.
Fig. 13-9
※ The disassembly and the reassembly are completed, however, carry out the following to check if the necessary
components have surely been assembled.
- 64 -
13-1-3 CHECKING THE RECOIL STARTER AFTER REASSEMBLY
(1) Pull the starter knob about 2-3 times.
(a) If the starter knob is too heavy to pull, check that each parts have been assembled as specified.
(b) If the ratchet does not work, check for missing parts such as the friction spring.
(2) Pull out the starter knob as far as it will go.
(a) If the starter rope remains in the rope slot in the reel, the spring may be over-stressed. To fix this, pull
out the starter rope approximately 30 cm, and, controlling the rotation of the reel with your thumb, allow
the starter rope to rewind about 1 or 2 turns.
(b) If the starter rope rewinds slowly or only partially, apply grease or oil to the rotary parts or the friction
surfaces. If this does not help, try winding up the spring 1 or 2 turns, taking care not to over-stress the spring.
(c) If there is a sound indicating that the spring is off the hook and the starter rope does not be wound
back, reassemble the recoil starter from the beginning.
13-1-4 OTHER GUIDES
SPRING
(1) If the spring escapes from the reel during
STARTER
REEL
disassembly
(a) Hook the outer end of the spring onto the gap
in the reel, and rewind the spring, holding the
spring with your fingers so as to prevent it from
springing out of the housing unit.
(Wear protective gloves when doing this.)
Hook the outer end of the
spring onto the gap in the reel.
Fig. 13-10
(b) Hook the inner end of the spring onto the
STARTER REEL
SPRING
projection on the starter case.
※ Refer to the assembly procedure for more
details.
(2) About lubrication
Lubricate the rotating and frictional parts and the
APPLY GREASE
spring with grease (heat-resistant grease
recommended) or engine oil when the starter is
disassembled and prior to long term storage.
STARTER CASE
Fig. 13-11
- 65 -
14. INSTALLATION
Installation has a decisive influence on engine life, ease of maintenance and inspection, frequency of inspection
and repair, running costs and other related aspects. Before installing the engine, be sure to plan the installation
with care, taking the points below into account.
14-1 INSTALLING
When installing the engine, pay special attention to the position of installation, the method for coupling with
working equipment, and the foundations and supports for the engine. Position the engine so that tasks such as
gasoline and oil replenishment and inspection, spark plug inspection, air cleaner maintenance, oil drainage
and so on can be carried out as easily as possible.
14-2 VENTILATION
An engine requires fresh air for cooling and for burning fuel. When an engine is covered with a bonnet or is operated
in an enclosed space, the temperature around the engine rises and this causes such problems as vapor lock, oil
deterioration, increased oil consumption, power loss, engine seizure, and reduced engine life, making it difficult for
the engine to function normally. It is thus necessary to install ducts and dampers to guide fresh air, so as not to
recycle the hot air used to cool the engine and to prevent the working equipment from heating up.
Be sure to keep the engine room temperature below 50°
C all year round and to prevent the accumulation of hot
air in the engine room.
14-3 EXHAUST EQUIPMENT
Exhaust gas is noxious. When operating the engine indoors, make sure that exhaust gases are discharged
outdoors. However, if the exhaust pipe is long, resistance increases and this lowers engine output. Therefore,
the longer the exhaust pipe the larger its inner diameter should be.
Exhaust pipe length:
Exhaust pipe length:
Less than 3 m
3-5m
Pipe inner diameter:
Pipe inner diameter:
30 mm
33 mm
The ideal solution is forced exhaustion (outdoors) by installing a blower on the exhaust pipe.
※ Install a safety cover on the exhaust pipe, muffler and other related parts.
14-4 FUEL SYSTEM
If the fuel tank is detached from the engine, the height from the bottom of the fuel tank to the fuel joint of the
carburetor should be between 5 cm and 50 cm.
When using a fuel pump, the bottom of the fuel tank can be up to 20 cm below the carburetor. Position the fuel
tank carefully because, when it is low, fuel is not fed to the carburetor and when it is high, it can cause an
overflow in the carburetor. When piping the fuel, the hose should be as short as possible and attention should
be paid to heat transmission, size, bending, leakage at hose joints and so on. Care should also be taken to
prevent air lock and vapor lock.
- 66 -
14-5 POWER TRANSMISSION TO DRIVE MACHINES
14-5-1 BELT DRIVE
Note the following:
• Use a V-belt rather than a flat belt.
• The drive shaft of the engine must be parallel to the drive shaft of the driven machine.
• The drive pulley of the engine must be in line with the driven pulley of the machine.
• Install the engine pulley as close to the engine as possible.
• If possible, span the belt horizontally.
• Disengage the load when starting the engine.
※ A belt tensioner or similar should be installed if no clutch is used.
14-5-2 FLEXIBLE COUPLING
When using a flexible coupling, run-out and misalignment between the driven shaft and the engine shaft
should be minimized.
The permissible margin of run-out and misalignment is specified by the flexible coupling manufacturer.
- 67 -
15. TROUBLESHOOTING
If the engine shows any sign of malfunction, the cause should be determined immediately and appropriate
countermeasures should be taken to prevent the problem from worsening. This section describes certain known
problems, their possible causes and appropriate countermeasures. Note, however, that the list of problems
presented here is not all. Generally speaking, since there is the possibility of multiple causes for a single problem,
please use your experience and common sense when deciding on what action to take.
15-1 ENGINE
The following three conditions must be fulfilled for satisfactory engine start.
1. The cylinder filled with a proper fuel-air mixture.
2. Good compression in the cylinder.
3. Good spark, properly timed, to ignite the mixture.
The engine cannot be started unless these three conditions are met. There are also other factors which
make engine start difficult, e.g., a heavy load on the engine when it is about to start at low speed, and a
high back pressure due to a long exhaust pipe.
Problem and possible cause
1. Ignition system problems
Remedy
1) Spark plug
・ Improper spark plug gap
・ Insulation defect
・ Carbon deposits
Adjust the gap
Replace
Clean
2) Ignition coil
・ Insulation defect or discontinuity
・ Poor contact or broken wire
Replace
Repair or replace
3) Improper air gap between ignition coil and flywheel Adjust
Starting difficulties
2. Fuel system problems
1) No fuel in fuel tank
Refill
2) Fuel hose clogged or pinched
Clean or replace
3) Air in fuel lines
Check and retighten joints
4) Poor quality gasoline or water in gasoline
Replace
5) Carburetor
・ Overflow
・ Clogged or damaged
・ Throttle valve malfunction
(does not close fully)
Adjust
Overhaul
Check and adjust
3. Engine core components 1) Insufficient tightening of cylinder head bolts
problems
2) Wearing of piston, piston rings and/or cylinder
Check and retighten
Repair or replace
3) Improper contact of valve and seat
Repair
4) Valve sticking
Repair
5) Improper valve clearance
Adjust
6) Leakage from intake manifold gasket
Retighten; replace gasket
7) Leakage from carburetor gasket
Retighten; replace gasket
8) Insufficient tightening of spark plug
Retighten
- 68 -
Problem and possible cause
Poor output
1. Insufficient compression
1) Loosen spark plug
Retighten; replace gasket
2) Leakage from cylinder head gasket
Retighten; replace gasket
3) Piston ring seizure or wear
Replace
4) Piston or cylinder wear
Repair or replace
5) Incorrect valve and seat contact
Repair or replace
6) Valve stem seizure
Repair or replace
7) Improper valve clearance
Adjust
2. Ignition system problems 1) Faulty spark plug
Replace
2) Faulty ignition coil
Replace
3) Improper air gap between ignition coil and
flywheel
Adjust
4) Demagnetization (flywheel magneto)
Replace
1) Carburetor clogged
Overhaul, clean
2) Fuel strainer and/or hose clogged
Clean or replace
3) Air in fuel lines
Check and retighten joints
4) Poor quality gasoline or water in gasoline
Replace
1) Air cleaner clogged
Clean or replace
2) Throttle valve malfunction
Repair or replace
1) Cooling air flow obstructed at inlet or cylinder
baffle portion
Clean
2) Poor quality engine oil
Replace
3) Lean fuel/air mixture
Check and adjust
carburetor
4) Excessive back pressure of exhaust system
Check and clean or replace
5) Overloading
Adjust to rated load
1) Low idling speed
Adjust
2) Slow system passage clogged
Check and clean
1) Air mixing from air intake system joints
Check and tighten;
replace gasket
3. Cylinder head
1) Gasket faulty (blow-by)
Replace
4. Valve system
1) Improper valve clearance
Adjust
2) Leakage from valve seat
Repair
3) Excessive clearance between valve stem and
guide
Replace
1) Weak spark
Check; adjust or replace
plug
3. Fuel system malfunction
4. Low air intake volume
Overheat
1. Engine
1. Carburetor system
2. Intake system
Rough Idling
Remedy
5. Ignition system
- 69 -
Problem and possible cause
High fuel consumption
Excessive engine oil consumption
1. Oil leakage
2. Oil up
1. Fuel system
1) Loose oil drain plug
Tighten
2) Faulty oil drain gasket
Replace
3) Loose main bearing cover bolts
Tighten
4) Faulty main bearing cover gasket
Replace
5) Crankshaft oil seal (front, rear) defect
Replace
1) Faulty piston oil ring
Replace
2) Piston ring seizure, wear or poor contact
Replace
3) Excessive wear of piston and/or cylinder
Replace
4) Faulty stem seal
Replace
5) Excessive oil level
Adjust oil level
6) Breather defect
Repair or replace
1) Clogged air cleaner
Clean or replace
2) Faulty needle valve and/or high fuel level in
float chamber
Repair or replace
3) Choke does not open fully
Repair or replace
2. Engine core components 1) Low compression
1. Ignition system problems 1) Loose ignition system wiring
Abnormal engine noise
3. Cylinder head
4. Valve system problems
Check and repair
Check and adjust load
and/or engine speed
2) Overcooling
2. Fuel system problems
Remedy
Inspect and tighten
2) Improper or faulty spark plug
Clean or replace
1) Lean or rich fuel/air mixture
Clean, adjust or replace
carburetor
2) Carburetor contamination
Overhaul or clean
3) Dirty or clogged fuel lines
Clean or replace
4) Air mixing from air intake system joints
Tighten; replace gasket
1) Carbon deposit in combustion chamber
Clean
2) Leakage from cylinder head gasket
Replace
1) Improper valve clearance
Adjust
2) Valve heat deterioration
Replace
3) Worn or broken valve spring
Replace
4)Improper valve timing
Adjust
- 70 -
ELECTRIC STARTER
Engine does not start
Does the
crank run?
NG
Does the
starter run?
Check battery charged
state and battery terminal
connection or corrosion
for any abnormality.
NG
Charge or replace the battery.
Repair connection or
corrosion of battery terminals.
NG
Key switch
Connected state
Check/repair wiring to the
starter magnetic switch.
Repair or replace starter
magnetic switch.
OK
Operation sound of
magnetic switch of starter
OK
NG
OK
Check settling of spring and
sliding of pinion.
Replace if pinion/ring gear
end face is worn.
Correction of pinion gap
OK
NG
Check engagement of
pinion and ring gear
OK
With starter alone, connect
the battery (+) terminal
and the M or K terminal of
the starter and check if
motor runs.
Check pinion roller clutch
for damage or replace.
OK
NG
Replace motor
(brush holder or armature).
OK
Check battery charged
state and battery terminal
connection or corrosion
for any abnormality.
Normal rotation?
NG
(Too slow)
There is any contact
failure of starter magnetic
switch. Please replace.
Check battery charged
state and battery terminal
connection or corrosion
for any abnormality.
NG
Charge or replace the battery.
Repair connection or
corrosion of battery terminals.
OK
OK
Check ignition system
and fuel system.
Check viscosity of engine
oil for any abnormality.
NG
Change the engine oil.
OK
Replace the starter with a
new one and check if it
runs.
NG
Check the engine interior.
S
OK
Repair or replace the
starter.
B
When the starter continuously runs
(Immediately remove the (-) terminal of the battery)
Motor does not stop even
when the key switch is
turned off.
Repair or replace the key switch
or starter magnetic switch.
- 71 -
K
M
Problem and check item
(1) Starter does not run or only “click” sound is heard.
1. Checking of
continuity of
wiring
Description
Check S terminal and B terminal
for deformation, looseness,
rusting, or dust sticking.
Carefully check inserting
method of the S terminal.
If not abnormal, set the key
switch to START position while
cranking (no ignition of engine)
and check if voltage is applied
to the S terminal and B terminal
of starter motor.
Remedy
KEY SWITCH
(+)
S
(-)
B
4. Checking of
magnetic
switch
(2) If voltage is applied to the S terminal
and B terminal, go to “2. Battery
checking.”
K
M
2. Battery checking Check battery voltage and specific
gravity of battery fluid.
[Voltage]
Normal value : 12.4 to 12.8V
Limit (charging required): 12.4V
or lower
Staring limit : 12V (at 20゚C)
[Specific gravity]
Normal value : 1.22 to 1.29
Limit (Charging required)
: 1.22 or lower
[Service life]
Variance in specific gravity
among cell
: 0.04 or more
3. Checking of
pinion operation
(1) When no voltage is applied to the S
terminal and B terminal, check
continuity of the terminals and key
switch and repair or replace if
necessary.
(1) Charge or change the battery when
voltage is lower than 12.4V or specific
gravity is lower than 1.22 (at 20°
C).
(2) If the wiring and battery are normal,
remove the star ter and go to “3.
GRAVITY METER
Checking of pinion operation.”
BATTERY
Check if the pinion operates or
sound of magnetic switch
contactor is heard.
If the pinion does not operate
or magnetic switch sound is not
heard, check continuity of each
coil of magnetic switch.
(1) If the pinion operates or contactor sound
is heard, step to “4. Checking of
magnetic switch (1).”
(1) Operate the magnetic switch
and check B-M terminals
(1) In case of no continuity
Contact continuity failure. Replace the
magnetic switch.
(2) In case of no continuity
Replace the magnetic switch.
(3) When continuity is OK
Step to “4. Checking of magnetic switch
(2).”
(2) When continuity is OK
Step to “5. Motor checking.”
(2) Check the magnetic switch
plunger and bobbin interior for
dust sticking or rusting.
5. Motor checking
Connect the (+) side of the
battery to the M terminal of
magnetic switch and check if the
motor runs.
(1) Clean the plunger. If the bobbin interior
is contaminated, replace the magnetic
switch.
(1) If the motor does not run, check electric
circuit inside the motor, field coil,
armature, and brush and replace faulty
parts.
(+)
(-)
M
- 72 -
Problem and check item
Description
Remedy
(1) Remove and check the starter. Check
or replace the pinion clutch if
necessary.
(2) Check battery charged state and
battery terminal connection or
corrosion for any abnormality.
If pinion and ring gear do not
engage with each other and
abnormal noise is heard between
end faces of pinion and ring gear,
check the starter pinion and ring
gear.
(1) Remove the starter and check pinion
and ring gear end faces. If worn,
replace the pinion and ring gear.
(2) In case of sliding fault of the pinion,
correct it.
(3) If shift lever or spring is deformed,
replace it.
(2) Starter runs but engine not
Check engaged Motor idles and engine does not
state of pinion and run.
ring gear.
(3) Both starter
and engine run,
but the engine
does not start.
RING GEAR
Check if the rotation speed is
normal or slow. If slow, check the
battery and engine oil viscosity.
PINION GEAR
(1) When the rotation speed is normal
Check the ignition system and fuel
system.
(2) When the rotation speed is slow
(a) Check the battery.
(b) Check the viscosity of engine oil. If
not normal, change the oil.
(c) If both (a) and (b) are normal
Remove and check the starter.
- 73 -
16. STANDARD REPAIR TABLES
“STD” in the following table is the parts dimension from the brand new engine or the spare parts.
Whereas, “Limit” shows the maximum allowance for the parts to be used on the engine.
If the measurement exceeds beyond the “Limit”, the part needs to be replaced and/or repaired.
16-1 STANDARD DIMENSIONS AND LIMITS OF USE
ITEM
Unit: mm (in.)
STD
Limit
EX13
EX17
EX21
EX27
0.05
(0.002)
0.1
(0.004)
Intake
Exhaust
EX13
EX17
EX21
EX27
0.7 - 1.0
(0.0276 - 0.0394)
---
Intake
Exhaust
EX13
EX17
EX21
EX27
5.500 - 5.518
(0.2165 - 0.2172)
---
Pin outer
diameter
D 1, D 2
EX13
EX17
EX21
EX27
5.970 - 5.980
(0.235 - 0.235)
5.9
(0.232)
Support
inner
diameter
D 3, D 4
EX13
EX17
EX21
EX27
6.00 - 6.018
(0.236 - 0.237)
6.05
(0.238)
CYLINDER HEAD
* Flatness
* Intake/exhaust valve seat
contact width
* Intake/exhaust valve guide inner diameter
* Rocker arm pin outer diameter
D1
D2
* Rocker arm pin support inner diameter
D3
D4
- 74 -
Unit: mm (in.)
ITEM
STD
CYLINDER
* Inner diameter
EX13
Standard
EX17
EX21
EX27
EX13
First
reboring
EX17
EX21
EX27
EX13
Second
reboring
EX17
EX21
EX27
EX13
EX17
EX21
EX27
* Roundness after reboring
EX13
EX17
EX21
EX27
* Cylindricity after reboring
PISTON
* Outer diameter at skirt in thrust
direction
EX13
Standard
EX17
EX21
EX27
EX13
Oversize
+0.25
EX17
EX21
EX27
EX13
Oversize
+0.50
EX17
EX21
EX27
- 75 -
Limit
58.000 - 58.019
(2.2835 - 2.2842)
67.000 - 67.019
(2.6378 - 2.6385)
75.000 - 75.019
To be rebored when
the difference between
max. and min. of
diameter reached to
0.1 (0.004).
(2.9528 - 2.9535)
58.250 - 58.269
(2.2933 - 2.2941)
67.250 - 67.269
(2.6476 - 2.6484)
Ditto
75.250 - 75.269
(2.9626 - 2.9633)
58.500 - 58.519
(2.3031 - 2.3039)
67.500 - 67.519
(2.6575 - 2.6582)
Ditto
75.500 - 75.519
(2.9724 - 2.9732)
Less than 0.01
(0.0004)
Less than 0.015
(0.0006)
57.980 - 58.000
57.89
(2.2827 - 2.2835)
(2.2791)
66.960 - 67.000
66.88
(2.6362 - 2.6378)
(2.6331)
74.980 - 75.000
74.89
(2.9520 - 2.9527)
(2.9484)
58.230 - 58.250
58.14
(2.2925 -2.2933)
(2.2890)
67.210 - 67.250
67.13
(2.6461 - 2.6476)
(2.6429)
75.230 - 75.250
75.14
(2.9618 - 2.9626)
(2.9583)
58.480 - 58.500
58.39
(2.3024 - 2.3032)
(2.2988)
67.460 - 67.500
67.38
(2.6559 - 2.6575)
(2.6528)
75.480 - 75.500
75.39
(2.9717 - 2.9724)
(2.9681)
Unit: mm (in.)
ITEM
PISTON
* Ring groove side clearance
STD
Top
Second
EX13
EX17
EX21
EX27
EX13
Oil ring
Coil exp
EX17
EX21
EX27
EX13
Oil ring
(three-piece)
EX17
EX21
EX27
* Piston pin hole
EX13
EX17
EX21
EX27
* Piston pin outer diameter
EX13
EX17
EX21
EX27
* Clearance between piston and cylinder
at skirt
EX13
Limit
0.035 - 0.080
0.15
(0.0014 - 0.0031)
(0.0059)
0.02 - 0.075
(0.0008 - 0.0031)
0.01 - 0.065
0.15
(0.0004 - 0.0026)
(0.0059)
0.01 - 0.065
(0.0004 - 0.0026)
0.060 - 0.165
(0.0024 - 0.0065)
0.0300 - 0.185
(0.0012 - 0.0073)
-------
0.0100 - 0.205
(0.0004 - 0.0081)
12.991 - 13.009
13.035
(0.5115 - 0.5122)
(0.5132)
15.991 - 16.009
16.035
(0.6296 - 0.6303)
(0.6313)
17.991 - 18.009
18.035
(0.7083 - 0.7090)
(0.7224)
12.992 - 13.000
12.960
(0.5115 - 0.5118)
(0.5102)
15.992 - 16.000
15.960
(0.6296 - 0.6299)
(0.6283)
17.992 - 18.000
17.960
(0.7083 - 0.7087)
(0.7071)
0.040 - 0.079
(0.0016 - 0.0031)
0.25
EX17
EX21
EX27
* Piston ring end gap
Top
Second
Oil
(Coil exp)
0.050 - 0.089
(0.0020 - 0.0035)
EX13
0.15 - 0.35
(0.0059 - 0.0138)
EX17
EX21
0.15 - 0.3
(0.0059 - 0.0118)
EX27
0.1 - 0.3
(0.0039 - 0.0118)
EX13
0.15 - 0.35
(0.0059 - 0.0138)
EX17
EX21
EX27
0.2 - 0.4
(0.0078 - 0.0157)
EX13
0.2 - 0.4
(0.0078 - 0.0157)
EX17
EX21
0.05 - 0.25
(0.0020 - 0.0098)
EX27
0.1 - 0.3
(0.0039 - 0.0118)
- 76 -
(0.010)
1.5
(0.0591)
1.5
(0.0591)
1.5
(0.0591)
Unit: mm (in.)
ITEM
STD
CONNECTING ROD
* Large end inner diameter
EX13
EX17
EX21
EX27
* Clearance between large
end and crank pin
EX13
EX17
EX21
EX27
* Small end inner diameter
EX13
EX17
EX21
EX27
* Clearance between small
end and piston pin
EX13
EX17
EX21
EX27
Limit
30.000 - 30.016
30.1
(1.1811 - 1.1817)
(1.1850)
34.500 - 34.516
34.1
(1.3386 - 1.3392)
(1.3425)
0.020 - 0.049
0.2
(0.0008 - 0.0019)
(0.0078)
13.010 - 13.021
13.08
(0.5122 - 0.5126)
(0.5150)
16.010 - 16.021
16.08
(0.6303 - 0.6307)
(0.6331)
18.010 - 18.021
18.08
(0.7091 - 0.7095)
(0.7118)
0.010 - 0.029
0.12
(0.0004 - 0.0011)
(0.0047)
* Large end side clearance
EX13
EX17
EX21
EX27
CRANKSHAFT
* Crank pin outer diameter
EX13
EX17
EX21
EX27
* Journal outer diameter
D1
EX13
EX17
EX21
EX27
D1
D2
D2
EX13
EX17
EX21
EX27
- 77 -
0.100 - 0.780
1.0
(0.0040 - 0.307)
(0.0394)
29.967 - 29.980
29.85
(1.1798 - 1.1803)
(1.1752)
34.467 - 34.480
34.35
(1.3570 - 1.3575)
(1.3524)
27.988 - 27.997
(1.1019 - 1.1022)
29.988 - 29.997
(1.1806 - 1.1810)
24.988 - 24.997
(0.9838 - 0.9841)
29.988 - 29.997
(1.1806 - 1.1810)
Unit: mm (in.)
ITEM
STD
Limit
CAMSHAFT
* Cam peak height (intake and exhaust)
Cam peak
height
EX13
EX17
EX21
EX27
Cam inner
diameter
D1,D2
EX13
EX17
EX21
EX27
Pin outer
diameter
D3,D4
EX13
EX17
EX21
EX27
Intake
EX13
EX17
EX21
EX27
Exhaust
EX13
EX17
EX21
EX27
Intake
EX13
EX17
EX21
EX27
Exhaust
EX13
EX17
EX21
EX27
Intake
EX13
EX17
EX21
EX27
Exhaust
EX13
EX17
EX21
EX27
29.028 - 29.128
28.98
(1.1428 - 1.1468)
(1.1409)
9.0 - 9.036
9.05
(0.3543 - 0.3557)
(0.3563)
* Cam sprocket inner diameter
* Pin (cam sprocket) outer diameter
D3
D4
D1
D2
INTAKE/EXHAUST VALVES
* Valve stem outer diameter
* Clearance between valve stem and
valve guide
* Valve clearance (in cold state)
- 78 -
8.953 - 8.975
8.95
(0.3525 - 0.3533)
(0.3524)
5.440 - 5.455
5.35
(0.2142 - 0.2148)
(0.2106)
5.426 - 5.444
5.35
(0.2136 - 0.2143)
(0.2106)
0.045 - 0.078
0.3
(0.0018 - 0.0031)
(0.0118)
0.056 - 0.092
0.3
(0.0022 - 0.0036)
(0.0118)
0.12 - 0.15
(0.0047 - 0.0059)
0.12 - 0.15
(0.0047 - 0.0059)
Unit: mm (in.)
ITEM
STD
Limit
VALVE SPRING FREE LENGTH
EX13
EX17
EX21
EX27
27.4
(1.0787)
VALVE SEAT ANGLE
(INTAKE AND EXHAUST)
* Valve cutter angle (a)
* Valve contact width (b)
Intake
Exhaust
EX13
EX17
EX21
EX27
a: 90°
b: 0.7 - 1.0
2.0
(0.0787)
(0.0276 - 0.0394)
CHAIN LENGTH
EX13
263.1
266.0
(10.3583)
(10.4726)
160N (16kgf.)
F
EX17
269.0
272.1
(10.5906)
(10.7126)
L
EX21
L
EX27
Compression pressure
Fuel consumption
Lubricant
284.9
(11.2165)
307.1
310.6
(12.0906)
(12.2284)
EX13
EX17
EX21
EX27
(kg・cm / 500 rpm)
3.5
4.0
4.0
4.0
(L / Hr)
1.2
1.6
1.9
2.6
2
Continuous load / 3600 rpm
281.7
(11.0906)
Capacity
(L)
0.6
1.0
Efficacy
(mL)
350
500
5 - 10
8 - 13
Consumption
(mL / Hr)
※ Oil consumption has been measured under-following condition :
・ Good break-in operation has been finished.
・ Oil : 10W-30 (Grade SE)
・ Load : Continuous load / 3600 rpm
- 79 -
16-2 TIGHTENING TORQUE
Tightening Torque
ITEM
N・m
kgf・cm
ft・lb.
25.0 - 27.0
250 -270
18.1 - 19.5
M8 × 68 flange bolt When replace to new
cylinder head and
flange bolts
28.0 - 30.0
280 - 300
20.3 - 21.7
M8 × 35 flange bolt
17.0 -19.0
170 - 190
12.3 - 13.7
EX13,17,21
13.0 - 15.0
130 - 150
9.4 - 10.8
EX27
17.0 - 20.0
170 - 200
12.3 - 14.5
Flywheel nut
59.0 - 64.0
590 - 640
42.7 - 46.3
Main bearing cover bolts
22.0 - 24.0
220 - 240
16.2 - 17.7
New
12.0 - 15.0
120 - 150
8.7 - 10.8
Re-tightening
23.0 - 27.0
230 - 270
16.6 - 19.5
Muffler nut
18.0 - 22.0
180 - 220
13.0 - 15.9
Ignition coil
7.0 - 9.0
70 - 90
5.1 - 6.5
Re-use
Cylinder head bolts
Connecting rod cap
bolts
Spark plug
- 80 -
17. MAINTENANCE AND STORAGE
The maintenance jobs described below apply to correct use of the engine under normal conditions.
The maintenance intervals mentioned in this section are not a guarantee that no maintenance is required
during those intervals.
For example, when the engine is used in dusty conditions, the air cleaner should be cleaned every day,
rather than every 100 hours.
17-1 DAILY MAINTENANCE (EVERY 8 HOURS OF USE)
MAINTENACE ITEMS
REASON / REMARKS
(1) Clean dust from engine.
(1) Dust can impair operation of various parts.
Governor linkage is especially sensitive to dust.
(2) Check for fuel leakage. Tighten or replace parts,
if necessary.
(3) Check all parts are securely fastened. Tighten,
if necessary.
(4) Check oil level and add up to full mark.
(2) Uneconomical and dangerous.
(5) Check that the air cleaner element is clean.
Clean or replace, if necessary.
(5) A clogged air cleaner can cause power loss
and malfunction.
(3) Looseness can result in vibration and
accidents.
(4) Running the engine with insufficient oil can
result in serious problems, including engine
seizure.
17-2 INSPECTION AND MAINTENANCE AFTER THE FIRST 20 HOURS
MAINTENACE ITEMS
REASON / REMARKS
(1) Change the crankcase oil.
(1) Sludge is deposited during running-in.
17-3 INSPECTION AND MAINTENANCE EVERY 100 HOURS (EVERY 10 DAYS)
MAINTENACE ITEMS
REASON / REMARKS
(1) Change the crankcase oil.
(2) Clean the air cleaner.
(3) Inspect the spark plug. Clean with gasoline or
polish with sandpaper if dirty.
(1) Contaminated oil quickens wear.
(2) A clogged air cleaner can cause engine
malfunction.
(3) A faulty spark plug can cause low power output
and poor starting performance.
17-4 INSPECTION AND MAINTENANCE EVERY 100 TO 200 HOURS (EVERY MONTH)
MAINTENACE ITEMS
(1) Clean the fuel strainer and fuel tank.
(2) Change the air cleaner element.
REASON / REMARKS
(1) Contaminated fuel can cause engine
malfunction.
(2) A clogged air cleaner can cause engine
malfunction.
- 81 -
17-5
INSPECTION AND MAINTENANCE EVERY 300 HOURS
MAINTENACE ITEMS
(1) Inspect the intake and exhaust valve clearance.
Adjust if necessary.
17-6
REASON / REMARKS
(1) Incorrect clearance can cause low power output
and engine malfunction.
INSPECTION AND MAINTENANCE EVERY 500 TO 600 HOURS (EVERY 6 MONTHS)
MAINTENACE ITEMS
REASON / REMARKS
(1) Remove the cylinder head and remove any carbon. (1) Carbon deposits can cause engine malfunction.
(2) Disassemble and clean the carburetor.
(2) A faulty carburetor can cause engine malfunction.
17-7 MAINTENANCE EVERY 1,000 HOURS (ANNUAL MAINTENANCE)
MAINTENACE ITEMS
(1) Overhaul the engine. Clean and correct the
engine parts, replacing if necessary.
(2) Replace the piston rings.
(3) Replace the fuel hose.
REASON / REMARKS
(1) Dirty, misaligned or worn parts can cause low
power output and engine malfunction.
(2) Faulty piston rings can cause low output power
and engine malfunction.
(3) To prevent fuel leakage and attendant dangers.
17-8 ENGINE STORAGE
(1) Carry out the maintenance jobs described in step 16-1 above.
(2) Drain fuel from the fuel tank and carburetor float chamber.
(3) To prevent rust in the cylinder bore, inject oil through the spark plug hole, pull the recoil starter knob
gently 2 or 3 times and then put back the spark plug.
(4) Pull the recoil starter knob until the resistance is heavy. Leave it in that position.
(5) Clean the exterior of the engine with an oiled cloth. Place a plastic cover or similar over the engine, and
store the engine in a dry place.
- 82 -
PRINTED IN THE USA
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