Http://motor.mortch.com

Mortch International Ltd
Service and Maintenance Manual
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2 STROKE 50cc
1E40QMB
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Mortch International Ltd
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Mortch International Ltd
Cylinder head nuts and exhaust pipe
bolts
Tighten at initially 1000 km(600 miles,2 moths),and
every 6000 km(4000 miles,12 months)
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If cylinder head nuts are not tightened to the
specified torque, may result in leakage of
compressed fuel-air mixture and reduce output,
tighten the cylinder head nuts in the following
procedures::
1. Remove the frame lower covers.
2. Remove the cylinder head cover bolt.
3. Remove spark plug cap.
4. Tighten the nuts evenly one by one to the
their specified torque. Tighten the nuts in the
order indicated.
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Tithtening torque:
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Cylinder head nut:
:15-18N.m
Cylinder and cylinder head
Remove carbon every 6000 km(4000
miles,12 months)
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Exhaust pipe bolt:
:15-18N.m
Carbon deposits in the combustion chamber and the
cylinder head will raise the compression ratio and may cause
preignition and overheating. Carbon deposited at the exhaust
port of the cylinder will prevent the flow of exhaust gases,
reducing the output. Remove carbon deposits periodically.
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Mortch International Ltd
SPARK PLUG
Neglecting the spark plug maintenance eventually leads to
difficult starting and poor performance. If the spark plug is used for a
long time, the electrode gradually burns away and carbon builds up
along the inside part. In accordance with the periodic table, the plug
should be removed for inspection, cleaning and to reset the gap.
Carbon deposits on the spark plug will prevent good sparking
and cause misfiring. Clean the deposits off periodically.
If the center electrode is fairly worn down, the plug should be
replaced and the plug gap set to the specified gap using a
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Thickness gauge
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thickness gauge.
Spark plug gap:0.6-0.7 mm (0.024-0.028 inch)
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Check the spark plug for burnt condition. If abnormal replace the spark
BPR7HS
TROCH
E8RTC
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plug as indicated in the chart.
REMARKS
If the standard plug is apt to get wet,
replace with the plug.
BPR9HS
E6RTC
Standard
If the standard plug is apt to
overheat, replace with the plug.
Tighten the spark plug to the specified torque.
Spark plug
Tightening torque:15-18N.m
NOTE:
To check the spark plug, first make sure that the fuel used is
unleaded gasoline, and if plug is either sooty with carbon or
burnt white, replace it.
Confirm the thread size and reach when replacing the plug.
FUEL LINE
Inspect at initially 1000 km (600 miles,2 months) and every
6000 km (4000 miles,12 months), replace every 4 years.
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E7RTC
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BPR8HS
Mortch International Ltd
ENGINE
CONTENS
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Engine components removal with the engine in place
Engine removal and remounting
Engine removal
Engine remounting
Engine disassembly
Engine components inspection and servicing
Bearings
Oil seals
crankshaft
automatic clutch inspection
cylinder head
cylinder
piston
reed valve
engine remounting
oil seals
bearings
bushings
crankshaft
crankcase
rear axle shaft
transmission
starter pinion and starter gear
Movable driven and clutch
Movable drive
Kicking starter
Piston
Oil pump and oil pump driven gear
Intake pipe
Magneto
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Engine components removable with the engine in place
The parts listed below can be removed and reinstalled without removing the engine
from the frame.
Engine left side
Kicking starter lever
Clutch brake pad kit
Driver left face
Driver belt right face
Carburetor
Intake pipe
Cylinder
Piston
engine right side
cooling fan
Magneto
Starter motor
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Cylinder head
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Worm wheel
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Oil pump
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Reed valve
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Engine center
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Driven face
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Electric starter gear
Super clutch
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V-belt
Mortch International Ltd
ENGINE ASSY.
Remove the muffler
Remove cooling fan cover
Remove cylinder cover
Remove cooling fan
Remove magneto nut with special tools.
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remove magneto rotor and half circle key
with special tools.
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remove magneto stator and paper gasket
remove oil pump
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Remove worm wheel and oil seal press board
remove cylinder head and
cylinder
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Place a cloth stopper beneath the piston
and remove the circlip with a plier.
remove the piston pin and piston.
Remove the kick starter lever.
Remove side cover
Remove movable ratchet wheel and clip
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Remove starting driven ratchet wheel by removing the nuts.
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Remove electric gear press board, electric
gear And super clutch
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Rmove fan⑤ and V-belt⑥.
Disassemble the movable drive
face⑦.
Remove starter motor
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Remove the clutch housing with the
special tool.
drain gear oil
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remove brake shoe⑤ and rear axle⑥。
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Remove the rear brake cam lever①,indicator
plate② and camshaft③.
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remove rear axle nut
remove rear wheel
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remove spring④
remove cotter pin⑤ and shaft⑥
remove main stand⑦
remove gearcase cover
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Remove paper gasket① and middle gear assy.②,
Remove output gear assy.③
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remove carburetor
remove intake pipe
remove reed valve and paper gasket.
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Remove crankcase fixing shaft
disassemble crankcase with special tools
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Remove crankcase with special tools
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Remove crankshaft bearing with special tools
Sliding shaft
Warning:
:use a new sliding shaft.
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Unscrew clutch shoe nut with special tools.
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Remove the nut while holding down clutch
shoe assy. by both hands as shown in the
illustration.
WARNING:Gradually back off the clutch shoe
assy. pressed down by hands to counter the clutch
sparing load. Releasing the hand suddenly may
cause the following parts to fly apart.
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①nut
②clutch shoe
③spring
Using a screwdriver or the like, pry up the
movable driven face spring guide.
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CAUTION:
:
Do not attempt to disassemble the clutch
shoe assy. Otherwise the clutch shoe may be
damaged.
● Remove the pins④, movable driven face⑤ and
fixed driven face⑥.
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Remove circlip
Remove bearing with special tool.
CAUTION:Replace the removed bearing
with a new one.
Remove bearing with special tool.
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Remove the spacer
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CAUTION:
:Replace the removed bearing
with a new one.
Remove the oil seal from the gearcase cover with the speical tool.
CAUTION:
:Replace the removed oil seal with a new one.
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Remove gearcase cover bearing
with special tool
Remove left crankcase oil seal
do it with special tool
warning:
:use a new oil seal
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remove left crankcase bearing with special tool
warning:
:use a new one
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remove left crankcase shock absorber
bushing with special tool
warning:
:use a new bushing
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wrap the oil seal with two appropriate size of
sheet irons and clamp it, shown as fig.
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Remove right crankcase oil seal with special tool
Warning:
:use a new oil seal
remove right crankcase bearing
sliding bearing
warning:
:use a new bearing
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ENGINE COMPONENTS INSPECTION AND SERVICING
BEARINGS
Clear bears with solvent and lubricate with
engine oil before inspecting.
Turn the inner ring and check to see that the inner
rieng turns smoothly. If it does not turn lightly, quietly
and smoothly, or if noise is heard, the bearing is
defective and must be replaced with a new one.
OIL SEAL
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Damage to the lip of the oil seal may result in leakage of the fuel-air mixture or oil.
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Inspect for damage and be sure to replace the damaged seal if found.
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CRANKSHAFT
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CRANKSHAFT RUNOUT
Support crankshaft by“V” block, with the dial gauge rigged
to read the runout as shown.
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Service limit:
:0.05mm(0.002in)
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Excessive crankshaft runout is often responsible for
abnormal engine vibration. Such vibration shortens engine
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life.
Condition of big end bearing
Turn the crankshaft with the connecting rod to feel the smoothness of
rotary motion in the big end. Move the rod up and down while holding
the crankshaft rigidly to be sure that there is no rattle in the big end.
Wear on the big end of the connecting rod can be estimated by
checking the movement of the small end of the rod. The
method can
also check the extent of wear on the parts of the connecting rod ‘s big
end. If wear exceeds the limit, replace connecting rod, crank pin
and crank pin bearing.
Service limit:
:3.0mm(0.12in)
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Mortch International Ltd
Connecting rod small end inside diameter
Measure the connecting rod small end diameter with a
caliper gauge.
Service limit:14.040mm
Automatic clutch inspection
1.Inspect initial engagement
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The scooter is equipped with an automatic clutch
and variable ratio belt drive transmission. The
engagement of the clutch is governed by engine RMPS
and centrifugal mechanism located in the clutch.
To insure proper performance and long lifespan of
the clutch, it is essentiall that the clutch engages smoothly
and gradually. Two inspection checks must be performed
to thoroughly check the operation of the drivetrain.
Follow the procedures listed.
2900r/min
±300r/min
2.Clutch “LOCK-UP” inspection
Perform the inspection to determine if the clutch is
engaging fully and not slipping.
Warm the engine to normal operating temperatures.
Connect the electric tachomter to the magneto lead
wire.
Apply the rer brake as firm as possible.
Briefly open the throttle fully and note the maximum
engine RPMs sustained during the test cycle.
CAUTION:
Do not apply full power for more than 10 seconds or
damage to the clutch or engine may occur.
LOCK-UP R/MIN
Standard
Tolerance
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5800r/min
±400r/min
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Standard
tolerance
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Warm up the scooter to normal operating
temperature.
Remove the right frame side cover.
Connect an electric tachmeter to the connecting portion
of the magneto lead wire (black with red tracer).
Seated on the scooter with the scooter on level ground,
increase the engine RPMs slowly and note the RPM at
which the scooter begins to move forward.
Tachometer
Mortch International Ltd
If the engine R/MIN doesn’t coincide with the specified r/min range, then disassemble the clutch.
Clutch shoe---inspect the shoes visually for chips, cracking, uneven wear and burning, and check the
thickness of the shoes with vernier calipers. If the thickness is less than the following service limit, replace them
as a set.
Clutch springs -----visually inspect the clutch springs for strectched coils or broken coils.
Service limit::2.0mm(0.08in)
CAUTION : clutch shoes or springs must
bechanged as a set and never individually.
Clutch wheel—inspect visually the condition of
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DRIVE BELT
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the inner clutch wheel surface for scrolling, cracks, or
uneven wear. Measure inside diameter of the clutch wheel
with inside calipers. Measure the diameter at several
points to check for an out-of-round condition as well as
wear.
Service limit:110.50mm(4.350in)
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Remove the drive belt and check for cracks, wear and
separation. Measure the drive belt width with a vernier calipers.
Replace it if the belt width is less than the service limit or and defect
has been found.
Service limit:16.0mm(0.630in)
CAUTION;Always keep the drive belt away from any
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Drive face
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geasy matter.
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Inspect the belt contact surface of the dirve faces for wear,
scratches or any abnormality . if there is something unusual,
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replace the drive face with a new one.
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Roller and sliding surface
Inspect each roller and sliding surface for
wear or damage.
Driving face spring
Measure the free distance of the driven face
spring. If the length is shoter than the service
limit, replace the spring with a new one.
service limit: 104.5mm(4.11in)
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Driven face pin and oil seal
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Turn the driven face and check to see that the driven faces
turn smoothly. If any stickiness or hitches are found,
visually inspect the lip of oil seal, driven face sliding
surface and sliding pins for wear or damage.
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Driven face
service limit:
:0.05mm(0.002in)
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Decarbon the combusion chamber.
Check the surface of the clinder head as shown in
the illustration for distortion with a straightedge and
thickness gauge, taking a clearance reading at several
places.
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Cylinder head
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inspect the belt contacting surface of bothdriven
faces for any scratches, wear and damage.
Replace driven face with a new one if there are any
abnormality.
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If the largest reading at any portion of the staightedge excees the limit, rework the surface by
rubbing it against emery paper laid flat on the surface plate in a lapping manner. The surface must
ge smooth and perfectly falt in order to secure a tight join: a
leaky joint can be the cause of reduced power output and
increased fuel consumption.
CYLINER
Decarbon exhaust port and upper part of the cylinder, taking care not to
damage the cylinder wall surface. The wear of the cylinder wall is determined from
diameter reading taken at
20mm from the top of the cylinder with a cylinder
gauge. If the wear thus determined exceeds the limit indicated below, rework the
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bore to the next oversize by using a boring machine or replace the cylinder with a
new one. Oversize pistions are available in two sizes: 0.5mm and 1.0mm.
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(cylinder gauge)
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service limit:
:40.075mm(1.5778in)
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after reworking the bore to an oversize, be sure to chamfer the edges of
ports and smooth the chamfered edges with emery paper. To chamfer,
use a scraper, taking care not to nick the wall surface.
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NOTE:
NOTE:
PISTON
cylinder and piston clearance
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Minor surface flaws on the cylinder wall durto seizure or
similar abnormalities can be corrected by grinding the flaws
off with fine-grain emery paper. If the flaws are deep grooves
or otherwise persist, the cyliner must be reworked with a
boring machine to the next oversize.
cylinder –piston clearance is the difference between piston diameter and
cylinder bore diameter. Be sure to take the maked diameter at right angles to the
A is prescribed to be 20mm from the skirt
piston pin. The value of elevation ○
end.
(micrometer)
service limit:
:39.885mm(1.5703in)
As a result of the above measurement, if the piston-to-cylinder clearance
exceeds the following limit, overhaul the cylinder and use an oversize piston,
replace both cylinder and piston. The measurement for the bore diameter should
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Mortch International Ltd
be taken in the intake-to-exhaust port direction and at 20mm from the cylinder top
surface.
Unit:mm
Standard
service limit
Cylinder
40.005-40.020
40.075
Piston
39.94-39.955
39.885
Cylinder to piston
0.06-0.07
0.120
Decarboning
Decarbon the piston and piston ring grooves, as illustration. After
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cleaning the grooves, fit the rings and rotate them in their respective
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grooves to be sure that they move smoothly. Carbon in groove is liable
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to cause the piston ring to get stuck in the groove, and the condition
G rind piston surface evenly with emery paper
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will lead to reduce engine power output.
A piston whose sliding surface is badly grooved ore scuffed
due to overheating must be replaced. Shallow grooves or minor scuff can be
Use a caliper gauge to measure the piston pin bore inside diameter,.
(Dial caliper)
Limit service: 12.30mm(0.4736in)
Piston pin outside diameter:
Use a micrometer to measure the piston outside diameter at three
positions.
(Micrometer(0-25mm))
service limit:11.980mm(0.4717in)
Piston rings
Check each ring for end gap, reading the gap with a thickness gauge shown in the
illustration. If the end gap is found to exceed the limit, indicated below, replace it
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If reading exceeds the following service limit, replace it with a new one.
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Piston pin bore
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removed by grinding with emery paper of about #400
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with a new one.
The end gap of each ring is to be measued with the ring fitted squarely into the cylidner bore and
held at the least worn part near the cylidner bottom, as shown in the illustration.
Service limit:0.75mm(0.030in)
As the piston ring wears, its end gap increases reducing
reducing engine power output becaust of the resultant blow
by through the enlarged gap. Here lies the importance of
using piston rings with end gaps with the limit. Measure the
piston ring free end gap to check the spring tension.
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service limit:3.6mm(0.14in)
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Fix the piston ring in the piston ring groove, measure
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the ring side clearance with the thicknes gauge while matching
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Standard clearance
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the sliding surface of piston and ring.
1st:
:0.04-0.06mm(0.0016-0.0024in)
2nd:0.02-0.04mm(0.0008-0.0016in)
the clearance A between reed valve and its seat
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Check
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Reed vakve
and the dimension B. If the clearance A is noted to exceed
least 1mm.
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0.2mm, replace the reed valve assembly. The dimension B is at
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Mortch International Ltd
ENGINE Reassembly
Reassembly is generally performed in the reverse
order of disassembly, but there are a number of
reassembling steps that demand or deserve detailed
explanation or emphasis. These steps will be taken up for
respective parts and components.
Oil seals
fit the oil seals to the crankcase following the
procedure below. Replace removed oil seals with new
ones.
Lubricate the edge of oil seal
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Install oil seal into crankcase carefully with special tool.
Oil seal installation
Install new bearing with special tool
Install bearing
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Bearing
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shock absorber bushing
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Install shock absorber bushing
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Press bearing into cankshaft
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Install crankshaft bearing
Install crankshaft
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Decide th length between the webs referring to the figure at
righ when rebuilding the crankshaft.
Standard width between webs::
:38±0.1mm(1.496±0.004in)
when mounting the crankshaft into crankcase, it is
necessaryto pull its left end into the crankcase with the
special tool.
CAUTION: Never fit the crankshaft into the the crankcase by driving it
with a plastic hammer. Always use the special tool, otherwise crankshaft
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alignment accuracy will be affected.
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CRANKCASE
Wipe the crankcase mating surfaces with
clraning solvent.
Apply evenly to the mating surface of the
right half of the crankcase
Tighten the crankcase screws securely.
Check if crankshaft rotates smoothly.
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Install gearcase bearing
Install new bearing and oil seal into gearcase cover with special tool, and tighten
anchor pin.
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install output axle
gearshift
install middle gear, position pin by installing middle gear
axle①, gasket② and thrust gasket③
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tighten each screw
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install gearcase cover into crankcase and lock
bolt.
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screw oil drain nut○
:4-7 N.m
tightening torque:
(0.4-0.7kg-m,3.0-5.0 Ib-ft)
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install the bearing② in the fixed driven face①
with the special tool.
install sliding bearing ③。
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Install the bearing ① with special tool
install the spacer ② and circlip③.
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NOTE:
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install the new oil seals④ and ⑤ to the
movable driven face with the special tool.
apply grease to the lip of oil seals and groove
of inside of movable driven face.
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When reinstalling the movable face to the fixed
face, make sure that the oil seal is positoned
properly.
install the pin ⑥ at three places on the driven
face hub.
Apply grease lightly to the cam part where the
pins are placed.
Install two O-RINGs⑦.
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Install the movable driven face seat①.
install the clutch shoe assembly② and nut
③.
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tighten the nut③ to the specified torque
with the special tool.
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tightening torque:
:40-60 N.M
(4.0-6.0kg.m 29.0-43.5Ib-ft)
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insert the V-belt between the driven faces as deep inside
possible while pulling the movable driven face all the way
outside to provide the maximum ble clearance.
CAUTION:
the belt should be positioned so that the arrows on the belt
periphery point the normal turning direction.
The V-belt contact face on the driven faces should be
thoroughly cleaned to be free from oil.
Thoroughly clean the clutch housing to be free from oil and
position it over the clutch shoe assembly.
tighten the clutch housing nut to the specified torque with
the special tool.
Torque:
:40-60 N.M
(4.0-6.0kg.m 29.0-43.5Ib-ft)
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Apply grease to all the sliding and rolling
surfaces for six roller weights. For each weight,
approximately 1.5g of grease should be used.
Install the movable drive face cover③.
NOTE:
1. Make sure that the movable drive plate is fully
positioned inside, or the weight roller may
come off.
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Mount the three dampers① on the movable
drive plate② and install it on the movable
drive face.
Position the O-RING on the movable drive
face.
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Insert the spacer④
Position the movable drive face subassembly
on the crankshaft as shown in illustration.
NOTE:
Thoroughly clean the belt contact to be free
from oil.
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Install the fixed drive fan①.
tighten the nut to the specified torque with
special tool.
Connecting rod fixer
Tightening torque:40-60N.M
(4.0-6.0kg-m, 29.0-43.5Ib-ft)
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fill grease in the groove provided inside
sliding surface of the kick driven gear and
install ② on the end of the crankshaft.
Wipe pff excess grease.
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Install washer③ and spring④.
NOTE:
When Installing washer③, face the resin
surface of washer to outside.
install the retainer⑤.
continue turning the fixed drive face⑥ by hand
until the belt is seated in and both the
drive and driven faces⑦ will move
together smoothly with slip.
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fill the final gear box with engine oil
up to the level hole.
Oil capacity: 90ml
tighten the oil level bolt to the
specified torque.
Tightening torque:9-15M.M
Starter assy.
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Inject lubrication into start bearing and
lubrication in the end of starter shaft
Install starter ratchet wheel and circlip
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LUBRICATION
Tighten starter shaft gasket
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Install the dowel pins①
install the new gaskets(② and ③)
apply pants to the clutch cover as shown in
the illustration.
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NOTE: INSTALL the kick starter lever as shown in the
illustration.
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Tightening toque:
:8-12N.M
(0.8-1.2kg-m, 6.0-8.5Ib-ft)
PISTON
install the piston rings on the piston.
The first and the second ring: keystone ring.
NOTE:
Position the ring so that the marking is on upside.
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cylinder, each ring in place should be so positioned as to hug
the locating pin as shown in illustration.
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it is extremely important that, when the piston is fed into the
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apply oil for the piston and install the piston to
the connecting rod.
NOTE:
The arrow mark ① on the piston head should point
the exhaust side.
The circlip should be mounted in such a
position that the mating ends of the circlip do
not coincide with the grovve portion of the
piston.
apply oil on the position and cyoinder wall
surfaces and install the cylinder over the piston
carefully.
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OUTSIDE
head
:18-28N.m
tightening torque:
nut
to
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install right crankcase oil seal press board
Oil pump
install oil pump into crankcase
torque:
:3-5N.m
(0.3-0.5kg-m, 2.3-3.7Ib-ft)
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install worm, and lubricater it with JINHONG
special lubrication.
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tighten the cylinder
specification.
Mortch International Ltd
Reed valve
install reed valve paper gasket.
Install reed valve
Install oil hose
Instake pipe
install intake pipe
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Magneto
clear crankshaft and magneto rotor
install half circle key
install paper gasket and stator coil, and then fix
them
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tighten to specified torque with special tool
specified torque:
:35-45N.m
(3.5-4.5kg.m,25.5-31.0Ib-ft)
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Mortch International Ltd
install cooling fan
install guiding cover
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install fan guiding cover
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install pipe screw ①
and screw for
tightening muffler to their specified
torque.
①:8-12N.m(0.8-1.2kg.m,6.0-8.5Ib-ft)
②:18-28N.m(1.8-2.8kg.m,13.0-20.0Ib-ft)
lubricate brake cam shaft with grease.
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Mortch International Ltd
SERVICING INFORAMTION
CONTENTS
Troubleshooting
Special tools
Thread parts tightening torque
Service data
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Mortch International Ltd
TROUBLESHOOTING
ENGINE
Complaint
Engine does not start,
or is hard to start.
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Symptom and possible causes
Compression too low
1. Excessively worn cylinder or piston rings.
2. Stiff piston ring in place.
3. Gas leaks from the joint in crankcase, cylinder or cylinder
head.
4. Damaged reed valve.
5. Spark plug too loose.
6. Broken, cracked or otherwise failed piston.
Plug not sparking
1. Damaged spark plug or spark plug cap.
2. Dirty or wet spark plug.
3. Defective CDI & ignition coil unit or stator coil.
4. Open or short n high-tension cord.
5. Defective ignition switch.
No fuel reaching the carburetor
1. Clogged hole in the fuel tank cap.
2. Clogged or defective fuel cock.
3. Defective carburetor float valve.
4. Clogged fuel hose or defective vacuum hose.
1. Carbon deposited on the spark plug.
2. Defective CDI & ignition coil unit.
3. Clogged fuel hose.
4. Clogged jets in carburetor.
5. Clogged exhaust pipe.
Noise appears to come from piston
1. Piston or cylinder worn down.
2. Combustion chamber fouled with carbon.
3. Piston pin, bearing or piston pin bore worn.
4. Piston rings or ring grooves worn.
Noise seems to come from crankshaft
1. Worn or burnt crankshaft bearings.
2. Worn or burnt conrod big-end bearings.
Engine idles poorly.
40
Replace.
Tighten
Replace.
Replace.
Clean and dry.
Replace.
Replace.
Replace.
Clean.
Clean or replace.
Replace.
Clean or replace.
Replace.
Clean.
Replace.
Replace.
Replace.
Replace.
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Noise seems to come from final gear box
Slipping clutch
Replace.
Repair or replace.
Repair or replace.
Clean.
Replace.
Clean.
Clean.
Clean.
or
Noisy engine.
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Engine stalls easily.
Remedy
Replace.
Replace.
Replace.
1.
2.
3.
1.
2.
Gears worn or rubbing.
Badly worn splines.
Worn or damaged bearing of drive shaft or rear axle shaft.
Worn or damaged clutch shoes.
Worn clutch drum.
Replace.
Replace.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Excessively worn cylinder or piston rings.
Stiff piston ring in place.
Gas leaks from crankshaft oil seal.
Spark plug gaps too wide.
Defective CDI & ignition coil unit.
Defective magneto stator coil.
Float-chamber fuel level out of adjustment in carburetor.
Clogged jets in carburetor.
Broken or damaged reed valve.
Replace.
Replace.
Replace.
Adjust or replace.
Replace.
Replace.
Replace.
Clean or adjust.
Replace.
Mortch International Ltd
Complaint
Engine
runs
poorly
in
high-speed
range.
Symptom and possible causes
1.
2.
3.
Excessively worn cylinder or piston rings.
Stiff piston ring in place.
Spark plug gaps to narrow.
4.
Ignition not advanced sufficiently due to poorly working CDI & ignition coil unit.
5.
6.
7.
Defective magneto stator coil.
Float-chamber fuel level too low.
Clogged air cleaner element.
8.
Clogged fuel hose, resulting in inadequate fuel supply to carburetor.
9.
Clogged fuel cock vacuum pipe.
Remedy
Replace.
Replace.
Adjust.
Replace.
Replace.
Adjust or replace.
Clean.
Clean and prime.
Clean.
Dirty or heavy
exhaust smoke.
1. Too much engine oil to the engine.
2. Use of incorrect engine oil.
Check oil pump.
Change.
Engine
power.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
1.
2.
3.
4.
5.
6.
7.
Replace.
Replace.
Replace.
Adjust or replace.
Clean.
Adjust or replace.
Clean.
Clean or replace.
Retighten or replace.
Replace.
Replace.
Replace.
Replace.
Clean.
Replace and clean.
Adjust or replace.
Retighten or replace.
Change.
Change.
Clean or replace.
Excessively worn cylinder or piston rings.
Stiff piston rings in place.
Gas leaks from crankshaft oil seal.
Spark plug gaps incorrect.
Clogged air cleaner element.
Float-chamber fuel level out of adjustment.
Clogged air cleaner element.
Fouled spark plug,
Sucking air from intake pipe.
Slipping or worn V-belt.
Damaged/worn rollers in the movable drive face.
Weakened movable driven face spring.
Too rich fuel/air mixture due to defective starter system.
Heavy carbon deposit on piston crown.
Defective oil pump or clogged oil circuit.
Fuel level too low in float chamber.
Air leakage from intake pipe.
Use of incorrect engine oil.
Use lf improper spark plug.
Clogged exhaust pipe/muffler.
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Engine
overheats.
lacks
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Mortch International Ltd
SPECIAL TOOLS LISTED BELOW FOR REMOVAL AND REINSTALLATION
NO.
DESCRIPTION
TOOL NUMBER
T01
“T”shape of sleeve
2
T02
sleeve tools(7mm,8mm,10mm,12mm,13mm)
3
T03
flywheel remover
4
T04
sleeve (18mm,24mm)
5
T05
screw remover
6
T07
cylinder pressure gauge
7
T08
piston pin remover
8
T09
9
T10
spark plug remover
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1
flywheel lockbolt remover
m
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clutch clamp
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③
①
②
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Mortch International Ltd
⑤
⑥
⑧
⑨
④
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⑦
⑩
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Mortch International Ltd
TIGHTENTING TORQUE O F SCREW THREAD PARTS
ENGINE
N.M
1-4
10-12
15-18
15-18
10-12
10-12
45-50
10-12
3-5
5-9
Right crankcase lock bolt
Bearing press board lock bolt
Cylinder double head bolt
Motor tightening bolt
Left crankcase cover lock screw
Left crankcase cover lock bolt
Main drive wheel face locknut
Driven wheel face locknut
Driven wheel face clutch locknut
Exceeding clutch outside lock screw
10-12
10-12
15-18
10-12
10-12
10-12
35-38
35-38
55-60
10-12
Electrical start idle press board screw
Gearcase lock bolt
Left crankcase discharging oil hole lock bolt
Left crankcase positioning pin shaft locknut
10-12
10-12
22-25
18-22
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ITEM
Cylinder guide cover tapping screw
Fan guide cover lock bolt
Cylinder cover locknut
Spark plug
Inlet pipe lock bolt
Cooling fan impeller lock screw
Flywheel lock bolt
Magneto stator coil lock screw
Magneto exciting lock screw
Oil pump lock screw
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Mortch International Ltd
SERVICE DATA
CYLINDER+PISTON+PISTON RING
Unit:mm(in)
ITEM
STANDARD
Piston
to
TOLERANCE
cylinder 0.06-0.07
0.120
clearance
(0.0024-0.0028)
(0.0047)
Cylinder bore
40.005-40.020
40.075
(1.5750-1.5756)
(1.5778)
39.94-39.955
39.885
(1.5724-1.5746)
(1.5703)
Cylinder diameter
Cylinder distortion
0.04
H
(0.0016)
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Cylinder head distortion
0.04
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st
(0.0016)
0.02~0.06mm
clearance
0.02~0.06mm
2en ring
ring
close
end 0.15-0.35
clearance
Piston
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Piston ring free cotter end 1 ring
(0.0059-0.0138)
ring
to
groove 1st ring
Piston pin bore
10.002-10.008
0.02~0.06(0.0008~0.0024)
0.02~0.06(0.0008~0.0024)
pin
outside 9.994-10.000
(0.3949)
(0.3935-0.3937)
CONNECTING ROD+CRANKSHAFT
9.98
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diameter
10.030
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(0.3938-0.3940)
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2en ring
(0.0315)
or
clearance
Piston
0.8
(0.3929)
ITEM
STANDARD
LIMIT
Conrod small end
13.995-14.006(0.5510-0.5514)
14.040(0.5528)
Conrod deflection
Conrod web to web width
Crankshaft runout
3.0(0.12)
38-38.1(1.496-1.500)
0.05(0.002)
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Mortch International Ltd
CLUTCH
Unit: mm(in)
ITEM
STANDARD
LIMIT
Clutch wheel inner diameter
112.00-112.15(4.410-4.415)
112.5(4.429)
Clutch shoe thickness
1.8(0.071)
1.2(0.005)
Clutch engagement
3000±300r/min
Clutch closedown
6000±300r/min
UNIT:mm(in) EXCEPT RATIO
TRANSMISSION SYSTEM+DRIVING CHAIN
ITEM
TOLERANCE
/
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/
/
16.8-17.2(0.6614-0.6772)
16.4(0.6457)
69(2.72)
64.5(2.54)
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Drive belt width
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Gear reduction ratio
H
Final reduction ratio
STANDARD
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Driven face spring free distance
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