Sym NCA250 Service Manual

PREFACE

PREFACE

 This shop manual describes the technical feature and

servicing procedures for the SANYANG NCA250.

 All information, illustrations, directions and

specifications included in this publication are base on
SANYANG NCA250.

 SANYANG reserves the right to make changes at any

time without notice and without incurring any
obligation whatever.

SANYANG INDUSTRY CO.,LTD.

SERVICE DIVISION

CONTENTS

CONTENTS

GENERAL INFORMATION ..........................................................................1

INSPECTION/ADJUSTMENT.......................................................................2

LUBRICATION SYSTEM..............................................................................3

ENGINE REMOVAL/INSTALLATION ..........................................................4

CYLINDER HEAD/VALVE............................................................................5

CYLINDER/PISTON......................................................................................6

CLUTCH/OIL PUMP/GEAR SHIFT ..............................................................7

A.C. GENERATOR.......................................................................................8

CRANK SHAFT/CRANK CASE/TRANSMISSION.......................................9

CARBURETOR.............................................................................................10

HEADLIGHT/STEERING/FRONT WHEEL/FRONT FORK ..........................11

REAR WHEEL/REAR SUSPENSION ..........................................................12

BATTERY/CHARGING SYSTEM.................................................................13

IGNITION SYSTEM.......................................................................................14

SWITCHES/HORN........................................................................................15

WIRING DIAGRAM.......................................................................................16

1.GENERAL INFORMATION

1-1

SERVICE RULES...............................1-1

SPECIFICATIONS..............................1-2

TORQUE VALUES.............................1-3

TROUBLE SHOOTING ......................1-4

SERVICE RULES:

(1)Use new packings, gaskets,O-rings and cotter

pins space and clipes whenever reassembling.

(5)Clean all removed parts in or with solvent, and

lubricate their sliding surfaces upon disassembly.

(2)When tightening bolts or nuts, begin on center or

larger diameter bolts and tighten them in criss-
cross pattern in two or more steps if necessary.

(6)Coat or fill parts with specified grease where

specified.

(3)Use genuine SANYANG parts and lubricants or

those equivalent. When parts are to be reused,
they must be inspected carefully to make sure they
are not damaged or deteriorated and in good
usable condition.

(7)Upon assembling, check every possible part for

proper installation and movement or operation.

(4)Use special tool when use of such a tool is
specified.

(8)Work safely and give your work your undivided
attention. Exchange signals as frequently as possi­ ble when a work involves two or more workers. Do
not run the engine unless the shop or working a re a
is well ventilated.

Symbol Marks:

:Apply engine oil.

NOTE: Things must be noticed.
CAUTION: Things that could cause damage to the

engine parts.

:Apply grease.

WARNING: Things that could cause damage to

the person or partner.

1.GENERAL INFORMATION

1-2

SPECIFICATIONS

ITEM NCA250

DIMENSIONS

Overall length
Overall width
Overall height
Wheel base
Ground clearance
Dry weight

2180mm
960mm
1130mm
1480mm
160mm

175kg

FRAME

Type
Front suspension and travel
Rear suspension and travel
Front tire size and tire pressure
Rear tire size and tire pressure
Front brake
Rear brake
Fuel capacity
Fuel reserve capacity
Caster angle
Front fork oil capacity

Double pipe
Telescope 165mm
Swing arm 63mm
90/90-18 2.25Kg/C ㎡

130/90-15 2.50Kg/C ㎡
Disk
Drum
14 liter

2.0 liter
26 °

160c.c

ENGINE

Type
Cylinder arrangement
Bore & stroke
Displacement
Compression ratio
Oil capacity
Intake valve opens
closes
Exhaust valve opens

closes
Valve clearance IN.
EX.
Idle speed

Air cooled 4 stroke O.H.C. engine
Double cylinders 15~ inclinde from vertical
53 x53mm

233.9c.c.

9.5:1

1.1 ~1.5 liter (1.3 liter for change)
0° BTDC
30 ° ABDC
35° BBDC

-5 ° ATDC

0.08mm

0.10mm

1500 rpm

DRIVE TRAIN

Clutch
Transmission
Primary reduction ratio
Gear ratio I

II
III
IV

V
Final reduction ratio
Gearshift pattern

Wet muti-plate type
5-speed internationl

3.83

2.46

1.777

1.333

1.083

0.913

2.285

1→N→2→3→4→5

ELECTRICAL

Ignition system
Ignition timing "F" mark
Full advance
Starting system
Alternator
Battery capacity
Fuse
Spark plug
Spark plug gap

C.D.I. unit
BTDC 15°±20° /1500rpm
BTDC 29.5°±2° /4000rpm
Electrical motor starter
A.C. generator
12V 9AH
20A×2/15A×2/10A×4
A6RTC

0.6~0.7mm

1.GENERAL INFORMATION

1-3

ENGINE

TIGHTEN LOCATION Q'TY THREAD DIA(mm) TORQUE(kgf·cm)
Oil plate pan screw
Crank shaft bolt
Crank shaft nut
Cylinder head nut
Cylinder head cover
Cam shaft sprocket bolt
Crank case bolt
L crank case cover bolt
Fly wheel bolt
A.C.G. scocket bolt
Start motor bolt
R crank case cove bolt
Cam shaft holder nut
Primary drive gear nut
Oil pump flat bolt
Clutch lock nut
Shift durm stopper
Shift cam bolt
Cam chain adjuster screw
Drain oil bolt
Gear shift spindle bolt

3
5
1
3
2
2

10

7
1
3
4

10

8
1
3
1
1
1
1
1
1

6
8
7
6
6
7
6
6

10

5
6
6
8

16

6

16

6
6
6

12

8

80~120

180~220

70~110
80~120
80~120
80~120
80~120
80~120

400~500

50~70
80~120
80~120

180~220
400~500

80~120

400~500

80~120
80~120
80~120

150~250
100~150

FRAME

TIGHTEN LOCATION Q'TY THREAD DIA(mm) TORQUE(kgf·cm)

Front wheel nut
Rear wheel nut
Rear fork pivot nut
Engine hanger nut
Handle pipe upper holder bolt
Steering stem nut
Front fork nut
Rear shock absorber
Rear brake torque link
Front fork top bridge
Rear fork bottom bridge
Final drive sprocket
Seat bolt
Drive sprocket bolt

1
1
1
3
4
1
1
4
1
2
2
4
2
2

14
14
14
10

8
22
22
10

8

7

8
10

8

6

600~800

1000~1200

800~1000

450~550

180~ 250

600~900
400~500
300~400
150~200
100~140
240~300
270~330
200~250
100~140

STANDARD TORQUE

TYPE TORQUE(kgf·cm) TYPE TORQUE(kgf·cm)

5 mm bolt, nut
6 mm bolt, nut
8 mm bolt, nut
10 mm bolt, nut
12 mm bolt, nut

45~60

80~120
180~250
300~400
500~600

5 mm bolt
6 mm bolt
6 mm flange bolt, nut
8 mm flange bolt, nut

10 mm flange bolt, nut

35~50

70~110
100~140
240~300
350~450

1.GENERAL INFORMATION

1-4

Torque specifications listed below for respective locations.
TROUBLE SHOOTING

A. HARD START OR CANNOT START

start engine with choke closed

engine knocks, but no
starting

follow the starter
keypoints to re-start

inspection adjustment

cause

loosen carburetor drain
screw, check inner side for
gasoline

enough gasoline supplied
for carbuertor

remove spark plug,insert it
into plug cap, check the
spark by touching engine
grid

test cylinder
compression

spark plug jump

spark weak or no spark

normal compression

pressure too low or no
pressure

engine dose not fire

spark plug dry

no gasoline in the tank
fuel tube between gasoline tank and
carburetor clogged.
float chamber fuel tube clogged
gasoline cover air hole clogged
fuel filter clogged
fuel filter screen clogged
gasoline auto fuel cup faulty

spark plug faulty
fouled spark plug
CDI unit fualty
pulse coil faulty
high voltage coil cable open or
short
high voltage coil open or short
main switch faulty

A.C.G. faulty

Battery faulty
valve too tight, no gap
valve seat faulty
cylinder, piston, piston ring
faulty
cylinder gasket leak
valve burnt out
valve timing faulty
crankcase leak when wmpress

Fuel tube clogged
muffler clogged
auto air cut poor action
inlet duct has air in
ignition timing incorrect
carburetor fuel adjusting
screw set faulty
air cleaner clogged

symptom

no gasoline supplied
for carburetor

remove and check the
spark plug again

spark plug wet

carburetor fuel level too high
auto air cut poor action
throttle excessively

1.GENERAL INFORMATION

1-5

B. ROTATION ROUGH (LACKS POWER)

symptom

inspection adjustment

cause

start engine and slightly
apply fuel

engine speed up

engine speed can't up

adjust ignition timing use
timing tester

valve adjusterpoor

ignition timing
correct

ignition timing
incorrect

valve clearance
correct

valve coearance
incorrect

compression pressure check

compression normal pressure to low

carburetor block check

remove spark plug

no clogged

block

air cleaner clogged
fuel tube clogged
air hole on the fuel tank cap blocked
exhaust tube clogged
auto air cut faulty
carburetor vacuum diaphragm worn
auto fuel cup faulty

faulty CDI unit
faulty A.C.Generator

fualty valve seat
cylinder, piston worn
gasket leak
valve timing incorrect

piston ring worn

remove and clean

remove dirt
spark plug improper heat range
spark plug clearance misadjustment

no fouled
discolored

dirt and color change

valve clearance misadjustment
valve seat worn

check crankcase oil level
for too much or dirt

oil lever normal

oil too much

too much oil
too little oil
oil no replacement

check cylinder head
lubrication

normal

abnormal

oil tube clogged
lean projection from oil pump

engine too hot

no overheating overheated

piston, cylinder worn
lean mixture
poor gasoline
carbon in burning chamber too much
ignition timing too early (C.D.I. faulty)

clutch slip

high speed
continue working

no knock shock knocks

carbon in burning chamber too much
poor gasoline
clutch slip
lean mixture
ignition timing too early(C.D.I.faulty)

1.GENERAL INFORMATION

1-6

C. ROTATION ROUGH (ESPECIALLY IN THE LOW SPEED AND IDLE SPEED)

symptom

inspection adjustment

cause

ignition timing
adjustment

faulty CDI unit
faulty A.C.Generator
valve gap adjust faulty

normal abnormal

adjust carburetor fuel
adjusting screw

adjust OK

adjust faulty

lean mixture(loosen screw)
rich mixture(tighten screw)

no air inlet

has air inlet

carburetor gasket
has air inlet

insulator plate gasket poor
carburetor locking nut loose
insulator plate gasket torn

vacuum tube crack
remove spark plug,
insert to the plug
cap, check spark by
toucning engine iron

g

rid.

sparking well poor sparking

poor or dirty spark plug
faulty CDI unit
faulty A.C.Genertor
poor ignition coil
spark plug cable open or short
poor main switch

good no good

vacuum tube damaged

air inlet duct clogged, damaged

1.GENERAL INFORMATION

1-7

D. ROTATION ROUGH (HIGH SPEED)

symptom

inspection adjustment

cause

ignition timing
adjustment

faulty CDI unit
faulty pulse generator

normal abnormal

valve clearance
adjustment

normal

abnormal

poor adjustment
valve seat faulty

normal abnormal

check auto fuel
cup for fuel
su

pp

lied.

too little fuel in the fuel tank
fuel tube, fuel filter clogged
air hole on the fuel tank colgs
auto fuel cup faulty

no blocked blocked

valve timing
adjusting
ins

p

ection

timing correct

timing incorrect

cam sprocket aligning marks incorrect

carburetor blocked

check valve spring

clean

good

spring broken
loose elasticit

y

faulty spring

1.GENERAL INFORMATION

1-8

E. POOR CHARGE (BATTERY OVER DISCHARGE OR OVER CHARGE)

symptom

inspection adjustment

cause

measure battery voltage.
and then start engine

reach battery life
faulty battery

battery voltage
can't rise

battery voltage rise to
normal value,after
engine stops, the voltage
return to original.

check voltage regulator
rectifier coupler

normal

abnormal

coupler poor contact
red wire open

hsa voltage no voltage

check the voltage between
voltage red wire
and frame body(grounding)
with mult-meter(+).(-)
terminals.

normal

abnormal

after engine starter, measure the
voltage between voltage regulaton
/rectifier red (+) wire and

green (-) wire connected with

frame body.

voltage over
normal

voltage normal

measure the resistance of
AC generator coil

check voltage regulator/
rectifier coupler for poor
contact.

coil faulty
connector.poor contact
AC generator white wire open

normal poor contact

voltage adjuster
white wire open

faulty battery

poor charge (over charge)

measure the resistance of
voltage adjuster unit

can't meet
s

p

ecification

faulty voltage
regulator/rectifier

Coupler poor contact.
green wire poor
grounding

1.GENERAL INFORMATION

1-9

F.SPARK PLUG NO SPARK

symptom

Inspection adjustment

cause

replace with new spark plug
and test again.

spark wear of

no spark

spark strong

original spark
plug faulty

Check spark cap and high
voltage cable for slack

no slack slack

spark plug cap
slack

check CDI unit plug for slack

normal abnormal

plug poor contact

Check the resistance
between the wires.
terminals of CDI unit.

normal abnormal

Check related portions

normal

abnormal

use CDI tester for CDI unit

normal

abnormal

use CDI tester to check
ignition voltage coil

abnormal

fualty main switch.
faulty trigger
magntic coil

faulty CDI unit

faulty IGN coil

control cable open
connector.socket
poor contact

poor pulse coil
poor IGN coil

2.INSPECTION/ADJUSTMENT

2-1

ENGINE

MAINTENANCE SCHEDULE.............2-2

SERVICE INFORMATION..................2-3

ENGINE OIL/OIL FILTER...................2-4

SPARK PLUG.....................................2-5

COMPRESSION TEST.......................2-6

VALVE CLEARANCE .........................2-7

IGNITION TIMING..............................2-8

CAM CHAIN TENSION ADJUSTMENT .......2-9

THROTTLE GRIP ADJUSTMENT......2-10

IDLING SPEED ADJUSTMENT..........2-11

FRAME

AIR CLEANER................................... 2-12

CLUTCH ADJUSTMENT................... 2-12

BRAKE ADJUSTMENT ..................... 2-13

DRIVE CHAIN ADJUSTMENT .......... 2-14

WHEELS/RIM .................................... 2-15

SUSPENSION................................... 2-16

STEERING........................................ 2-17

BATTERY.......................................... 2-17

HEAD LIGHT AIM.............................. 2-18

STOPLIGHT SWITCH....................... 2-18

2.INSPECTION/ADJUSTMENT

2-2

MAINTENANCE SCHEDULE

Maintenance
kilometer

300KM

Every

1000KM

Every

3000KM

Every

6000KM

Every

12000KM

Item

Check Items

Maintenance
Interval

NEW 1 Month 3 Months 6 Months 1 Year

1

Air cleaner I C R

2

Gasoline filter I C R

3

Oil filter C Replacement for every 5000KM R

4

Oil filter screen C Cleaning for every 5000km C

5

Engine Oil R Replacement for every 1000KM R

6

Wheels tires I I

7

Battery I I

8

Brake and operation free play I I

9 Steering stem bearing

I

10

FR./RR. Cushion I I

11

Screws/nuts I I

12

Spark plug I R

13

Clutch I I

14

Frame of lubrication L

15

Exhaust muffler I I

16

Carburetor I I

17

Ignition timing I I

18

Emission I I

19

Idle speed I I

20 Gasoline system

I I

21 Throttle cable

I I

22 Engine bolt torque

I I

23 Deposit of exhaust outlet

I

24

Cylinder head/cylinder
Piston exhaust system deposit

I

25 Cam chain

I I

26 Valve clearance

I I

27 Light/electrical appliance/Meter

I I

28 Side stand﹠Spring

I I

The table is refered to the driving distance about 1000km per month

I-inspection, cleaning, adjustment or replacement (if necessary)R-replacement C-leaning L-lubrication
REMARK: Ridden in unusually dusty areas, require more frequently air filter element cleaning.

2.INSPECTION/ADJUSTMENT

2-3

SERVICE INFORMATION

SPECIFICATLON

ENGINE

Oil capacity 1.1～1.5 liter

Spark plug gap A6RTC
Spark plug gap 0.6-0.7mm
Valve clearance IN 0.08mm

EX 0.10mm

Cylinder compression 12.5kg/c ㎡±2kg/c ㎡

FRAME

Clutch lever free play 10-20mm
Drive chain stack 10-20mm
Front brake lever free play 10-20mm

Rear brake pedal free play 20-30mm
Throttle grip free play 2-6mm

SPECIAL TOOL

Valve clearance adjuster

TORQUE VALVES

Right crankcase cover 80-120 kgf·cm
Front fork top bridge bolt 100-140 kgf

·cm

Front fork bottom bridge bolt 200-250 kgf

·cm

Rear wheel axle nut 400-550 kgf

·cm

Rear shock absorber nut 300-400 kgf

·cm

Rear fork pivot bolt 350-450 kgf

·cm

2.INSPECTION/ADJUSTMENT

2-4

OIL/OIL FILTER

OIL LEVEL CHECK

Start and warm up the engine for few minutes,then
stop the engine.
Check the oil level with oil level gauge after a few
minutes.
If the oil level is near the lower mark,fill the
crankcase to the upper level mark with the
recommended grade oil.

OIL REPLACEMENT

NOTE:

Remove the drain bolt, and drain the engine oil.

NOTE :

Fill the crankcase up to the upper level mark on the
oil level gauge with the recommended oil:15W-40
API:SH/CD

Drain the engine oil while the engine is warm.

Make sure that the drain bolt washer is in good
condition.

DRAIN BOLT

2.INSPECTION/ADJUSTMENT

2-5

OIL FILTER SCREEN CLEANING

Remove the drain bolt, and drain the engine oil.
Remove the right crankcase cover.
Remove the pump.
Clean the oil filter screen with compressed air.
Assemble the filter screen in reverse order of
disassemble.

SPARK PLUG

Disconnect the spark plug cap and remove the spark
plug .

Visually inspect the spark plug electrodes for wear.
The center electrode should have square edges and

side electrode should have a constant thickness.
Discard the spark plug if there is apparent wear or if

the insulator is cracked and/or chipped .If the spark
plug deposits can be removed by sandblasting or wire
brushing,the spark plug can be reused.

Inspect the gap with a feeler gauge and adjust by
bending the side electrode.

Standard gap:0.6-0.7mm

NOTE:

To install turn finger tight then tighten with a spark
plug wrench.

OIL FILTER

2.INSPECTION/ADJUSTMENT

2-6

COMPRESSION TEST

Warm up the engine.
Stop the engine .Remove spark plug .Insert the

compression gauge.
Push in the choke lever .Open the throttle grip fully.

Electrical start engine several times.

NOTE:

Compression:9.5kg/c ㎡±1kg/c ㎡
Low compression can be caused by:

 Improper calve adjustment.
 Valve leakage .
 Blown cylinder head gasket.
 Worn piston rings or cylinder.
 Worn piston.

High compression can be caused by:

 Carbon deposits in combustion chamber or on

piston head.

 Watch for compression leaking at the gauge

connection.

 Crank the engine until the gauge reading stops

rising .The maximum reading is usually reached
in several times.

ELECTRICAL
START ENGINE

2.INSPECTION/ADJUSTMENT

2-7

VALVE CLEARANCE

NOTE:

Remove the timing inspection hole cap and crankshaft
hole cap.
Rotate the generator rotor counterclockwise and align
the “T”mark on the generator rotor with the index mark
in the left crankcase
(piston must be at T.D.C.of the compression
stroke).

Inspect the intake and exhaust valve clearance by
inserting a feeler gauge between the adjusting screw
and valve stem,valve clearance:
Intake: 0.08mm
Exhaust: 0.10mm
Adjust by loosening the lock nut and turning the
adjusting screw until there is a slight drag in the feeler
gauge.

NOTE:

Inspect and adjust the valve clearance while the
engine is cold.

Inspect the valve clearance again after tightened the
lock nut.

ALIGN
MARK

ALIGN
MARK

ADJUSTING
SCREW

LOCK NUT

2.INSPECTION/ADJUSTMENT

2-8

Install the valve adjuster caps and generator cap.

NOTE:

IGNITION TIMING

Use the standard tester to check the ignition timing.
Spark plug inspection and adjustment.
Replace the coil if there is no sparks at plug.

IGNITION TIMING INSPECTION

Remove the generator cover and check the ignition
timing with a timing light.
Timing is correct if the index mark aligns with the
“F”mark within ±3°at 1500rpm.
Ignition timing :10°BTDC/1500rpm.
Ignition coil continuity test :
Check the resistance of the primary coil
and secondary coil.

1.Primary coil 0.31±0.03Ω

2.Secondary coil 4.0±0.4kΩ

Check the O-ring for damage and spread oil before
installing the caps.

The C.D.I.ignition timing is not adjustable.
If the ignition timing is not correct ,check the C.D.I.unit
and A.C.generator and replace any faulty parts.

O-RING

2.INSPECTION/ADJUSTMENT

2-9

Inspect the C.D.I unit with C.D.I tester.
Replace the faulty C.D.I unit.

SWITCH C.D.I. normal C.D.I faulty

1. OFF

2. P

3. EXT

4. ONI

5. ONZ

no sparks
no sparks
no sparks
sparks
sparks

-------

------­sparks
no sparks
no sparks

CAM CHAIN TENSIONER
ADJUESTER

The cam chain tension is kept by the tensioner
push rod that is compressed by the spring.

CAUTION:

If remove any parts that is related with the cam
chain ,remove the cam chain tensioner adjuester
first.

CAM CHAIN TENSIONER ADJUESTER

2.INSPECTION/ADJUSTMENT

2-10

CARBURETOR
THROTTLE GRIP FREE PLAY

Check throttle grip free play.
Free play:2-6mm

THROTTLE GRIP ADJUSTMENT

Loosen the lock nut and turn the adjuster to adjust.

ADJUSTER NUT

2.INSPECTION/ADJUSTMENT

2-11

IDLING SPEED ADJUSTMENT

Warm up the engine.
Turn the stop screw to obtain the idling speed of
1100rpm.
Turn the air screw to the maximum speed,then turn
the stop screw to obtain the specified idling speed.
Idling speed:1500±100 rpm

NOTE:

Turn the air screw clockwise for making fuel –air
mixture lean.
Turn counterclockwise for rich.

STOP
SCREW

AIR SCREW

2.INSPECTION/ADJUSTMENT

2-12

AIR CLEANER

Remove the left side cover.
Remove the air cleaner cover.
Remove the air cleaner element.

NOTE:

Clean the cleaner element periodically.(Refer to
maintenance schedule.)

Assemble air cleaner element in reverse order of

disassemble.

CLUTCH ADJUSTMENT

CLUTCH LEVER FREE PLAY

Measure the clutch free play at the tip of the clutch
lever.
Free play :10-20mm

SCREWS

AIR CLEANER ELEMENT

2.INSPECTION/ADJUSTMENT

2-13

FREE PLAY ADJUSTMENT

Loosen the lock nut and turn the adjuster.
Turn the adjuster ,clockwise for decreasing the free
play ,counterclockwise for increasing the free play.

.

Or adjust clutch lever adjuster nut.

BRAKE ADJUSTMENT

FRONT BRAKE LEVER FREE PLAY

Measure the brake free play at the tip of the brake
lever.
Free play:10-20mm

BRAKE PAD WEAR INSPECTION

Check for brake pad wear by operating the bake lever.
Check the brake pads for wear by looking through the
slot indicated by the arrow cast on the caliper
assembly.
Replace the brake pads if the wear line on the pads
reaches the edge of the brake disc.

ADJUSTER
NUT

LOCK
NUT

LEVER ADJUSTER NUT

10~20mm

2.INSPECTION/ADJUSTMENT

2-14

REAR BRAKE PEDAL FREE PLAY

Measure the brake pedal free play before the brake
start to engage.
Free play :20-30mm

REAR BRAKE PEDAL ADJUSTMENT

Turn the adjuster clockwise for decreasing the
clearance ,counterclockwise for increasing the
clearance.

CAUTION:

Keep the adjuster at the right position.

DRIVE CHAIN ADJUSTMENT

Place the motorcycle on its side stand and shift the
transmission into neutral.
Remove chain cap and check the drive chain slack by
moving up and down with the fingers.
Chain slack:10-20mm

20~30mm

A

DJUSTER NUT

10~20mm

2.INSPECTION/ADJUSTMENT

2-15

Loose the rear wheel axle nut for adjusting.
Turn the adjusting nuts on both adjusters as
necessary.

CAUTION:

Tighten the axle nut.

TORQUE:1000-1200 kgf·cm

Recheck the drive chain slack and free wheel rotation.
Lubricate the drive chain with chain lubricant.

WHEEL/RIM

Stand the motorcycle,check the tires for
cuts,imbedded nails,or other sharp objects.
Check the tire pressure.

One rider

Front 2.25 kg/c ㎡
Rear 2.50 kg/c ㎡

Cold tire

Two riders
pressure

Front 2.50 kg/c ㎡
Rear 2.50 kg/c ㎡

Max.load 120kg

Tire size

Front 90/90-18
Rear 130/90-15

Min. depth of tread

Front 1.5mm
Rear 2.0mm

A

DJUSTING NUTS

2.INSPECTION/ADJUSTMENT

2-16

SUSPENSION

FRONT SUSPENSION

Check the action of the front forks by compressing
them several times with the front brake applied .
If there are abnormal noises or rattles ,check all the
fasteners and tighten them to the specified torque.
TORQUE:
Front fork top bridge bolt :100-140 kgf

·cm

Frint fork bottom bridge bolt :240-300 kgf

·cm

Axle nut:600-800 kgf

·cm

REAR SUSPENSION

Check for abnormal noises and leaks by compressing
the rear suspension several times.
Check the rear suspension nut for loosing
Torque:300-400 kgf

·cm

Move the rear wheel side ways with force to see if the
swing arm bushings are worn.
Rear fork torque:800-1000 kgf

·cm

2.INSPECTION/ADJUSTMENT

2-17

STEERING

Raise the front wheel off the ground and check that
the handlebar rotates freely.If the handlebar moves
unevenly ,binds or has vertical movement,adjust the
steering head nut.

BATTERY

Inspect the battery fluid level ,if the fluid level nears
the lower level mark,fill with distilled water to the upper
level mark .
Clean the battery terminals with warm water.
Check the specific gravity of the battery
electrolyte.(13-3)

NOTE :

Do not overfill. Add only distilled water.
Tap water will shorten the service life of the
battery.

WARNING:

Keep the electrolyte away from eyes ,skin and
clothes. If touched it ,wash them with clean
water quickly.

2.INSPECTION/ADJUSTMENT

2-18

HEADLIGHT AIM

Adjust vertically by turning headlight up and down with
the headlight bolts loosening.
Fasten the bolts after adjustment.

STOPLIGHT SWITCH

The stoplight should come on when the brake pedal is
depressed 20mm from the standard pedal position.If
the action is abmormal, adjust by turning the stoplight
switch adjusting nut.

NUTS

STOPLIGHT SWITCH

A

DJUSTING NUT

3.LUBRICATION SYSTEM

3-0

CAM SHAFT

OIL LINE OF
CAM SHAFT

PISTON

OIL FILTER

OIL ORIFICE OF
CRANKSHAFT

OIL PUMP

MAIN SHAFT

COUNTER SHAFT

3.LUBRICATION SYSTEM

3-1

TROUBLE SHOOTING...................... 3-1 SERVICE INFORMATION.................3-1

TROUBLE SHOOTING

OIL LEVEL TOO LOW

1. Natural consumption

2. Oil leaks

3. Worn piston rings

OIL CONTAMINATION

1. Oil not changed often enough

2. Faulty cylinder head gasket

OIL PRESSURE TOO LOW

1. Oil filter clogged

2. Oil pump damaged

OIL PRESSURE TOO HIGH

1. Oil filter or line clogged

2. Oil not recommended

NO OIL PRESSURE

1. Oil level too Iow

2. Oil pump damaged

SERVICE INFORMATION

NOTICE:

Inspection and service of oil pump can be serviced
with the engine installed on the frame.
Oil pump service --- 7-9
Oil filter cleaning --- 2-4 ~ 2-5

SPECIFICATIONS

Oil capacity
Oil recommended
Oil pump delivery

1.1~1.5 liter
SAE 15W-40 API:SH/CD

3.5 liter above / min. / 4600rpm

4.ENGINE REMOVAL/INSTALLATION

4-1

SERVICE INFORMATION..................4-1

ENGINE REMOVAL ...........................4-2

ENGINE INSTALLATION.................. 4-5

SERVICE INFORMATION

GENERAL INSTRUCTIONS

The following parts can be serviced with the engine installed on the frame:

 Generator
 Clutch
 Oil pump
 Cam shaft / Rocker arm
 Shift spindle
 Cam chain tensioner

The following parts must be serviced with the engine removed off the frame:

 Cylinder head
 Cylinder
 Piston
 Crankshaft
 Transmission

During removal and installation, jack or adjustable support is required to maneuver the engine.

TORQUE VALUES

Engine hanger 10mm bolt / nut 450-550 kgf·cm
Drain bolt 300-500 kgf·cm
Gearshift pedal bolt 80-120 kgf·cm

4.ENGINE REMOVAL/INSTALLATION

4-2

ENGINE REMOVAL

Drain the engine oil.
Disconnect the fuel tubes and all connect tubes.
Remove the right and left side covers.

Remove the gear change pedal and left crank case
rear cover.

Disconnect the A.C. generator wire of the connector
and remove the generator wire.

LEFT CRANKCASE
RR.COVER

GEAR CHANGE

A

RM

A

.C. GENERATOR

WIRE

4.ENGINE REMOVAL/INSTALLATION

4-3

Remove the clutch cable.
Remove the spark plug cap.
Remove the muffler.

Loosen carburetor clip.
Separate the carburetor pipe and the cylinder head by
removing the attaching bolts.
Remove the crankcase breather tube.

Loosen the rear wheel axle nut.
Loosen the drive chain adjusting nut and push the rear
wheel forward.
Remove the drive chain clip, and remove the drive
chain.

CLIP

BREATHER TUBE

CLUTCH CABLE

WHEEL AXLE NUT

ADJUSTING NUT

4.ENGINE REMOVAL/INSTALLATION

4-4

Remove the front engine hanger bolt.

NOTE:

Places jack or padded block under the engine before
removing the front engine hanger.

Disconnect the starter motor wire.

Remove the 10mm bolts of the rear engine hanger.

Remove the engine.

NOTE:

Prevent damage to wire harnesses and cables during
operation.

FRONT ENGINE HANGER
BOLT

BOLTS

4.ENGINE REMOVAL/INSTALLATION

4-5

ENGINE INSTALLATION

Follow the reverse procedure of removal to install the
engine.
Notice the following items during installation:

 Route all wire harnesses and cables properly.
 Adjust the throttle grip free play (P2-10)
 Adjust the clutch lever free play (P2-12)
 Adjust the drive chain slack (P2-14)
 Fill the crankcase with the recommended grade oil

to the proper level.

SAE 15W-40 APl: SH / CD

5. CYLINDER HEAD/ VALVE

5-1

TROUBLE SHOOTING.......................5-1

SERVICE INFORMATION..................5-2

CAM SHAFT REMOVAL ....................5-3

CYLINDER HEAD/ROCKER ARM REMOVAL .....5-4

CYLINDER HEAD DISASSEMBLY ....5-6

VALVE/VALVE GUIDE INSPECTION........5-7

VALVE GUIDE REPLACEMENT........5-8

VALVE SEAT INSPECTION/REFACING...5-9

VALVE SEAT GRINDING...................5-10

CYLINDER HEAD ASSEMBLY..........5-13

CYLINDER HEAD INSTALLATION....5-14

CAM SHAFT INSTALLATION ........... 5-15

TROUBLE SHOOTING

LOW COMPRESSION

1. Valve

Incorrect valve clearance
Burned or bent valves
Incorrect valve timing
Broken valve spring

2. Cylinder head

Leaking or damaged head gasket
Warped or cranked cylinder head

HIGH COMPRESSION

1. Excessive carbon buildup on piston or combustion chamber.

ABNORMAL NOISE

I. Incorrect valve clearance

2. Broken valve spring

3. Worn rocker arm or camshaft

4. Loose or worn cam chain

5. Worn cam chain tensioner

6. Worn cam sprocket teeth

5.INSPECTION/ADJUSTMENT

5-2

SERVICE INFORMATION

GENERAL INSTRUCTIONS

Camshaft, rocker arm shaft and rocker arm can be serviced with the
engine installed on the frame.
Camshaft lubrication oil is fed to the cylinder head through an oil
control orifice in the engine case.
Be sure this orifice is not clogged and the O-ring and dowel pins are in
place before installing the cylinder head.
During assembly, apply molybdenum disulfide grease to the camshaft
bearings, and pour clean engine oil into the cylinder head.

TORQUE VALUES

Cylinder head bolt 280-300 kgf·cm
Cylinder 6mm bolt 140 -180 kgf

·cm

Cam sprocket 80-120 kgf

·cm

SPEClFICATIONS

ITEM STANDARD SERVICE LIMIT

IN 32.382mm 31.25mm below

Cam lift

EX 31.987mm 30.87mmbelow

Camshaft

Runout 0.02mm

Rocker arm I.D. I.D. 10.000～10.015mm 10.015mm above

Rocker arm shaft O.D. 9.978～9.987 mm 9.978mm below

Outer 35.7～36.3mm 35mm below

Free length

Inner 29.7～30.3mm 28mm below

Outer

→29.65mm 130.5±6.5N

→23.45mm 330.0±16N

Valve
spring

Stall length

Inner

→26.65mm 69.0±5.52N

→20.45mm 236.0±11.8N

Valve clearance

(IN)0.06±0.02mm

(EX)0.10±0.02mm

IN 5.450～5.465mm 5.42mm

O.D.

EX 5.430～5.455mm 5.40mm

IN 5.475～5.485mm 5.50mm

Guide I.D.

EX 5.475～5.485mm 5.50mm

IN 0.010～0.035mm 0.08mm

Stem to guide

Clearance

EX 0.03～0.055mm 0.10mm

Valve
guide

Valve seat width 1.45～1.15mm 1.6mm

5. CYLINDER HEAD/ VALVE

5-3

CAMSHAFT REMOVAL

NOTE:

The camshaft, rocker arm and rocker arm shaft can
be serviced with the engine installed on the frame.

Remove the 6mm special bolts.
Remove the R/L cylinder head side cover and cylinder
head side.
Remove the cylinder head cover.

Remove the crankshaft hole cap and the timing
inspection hole cap. Rotate the generator rotor
counterclockwise and locate the piston at the T.D.C. of
the compressing stroke.
Remove the cam chain adjuster screw.

Remove the four holder nuts.
Remove the holder.
Remove the camshaft.

CAUTION:

Support the cam chain to keep it from falling into the
crankcase.

special bolts

nut nut

5.INSPECTION/ADJUSTMENT

5-4

CYLINDER HEAD

REMOVAL

Remove the 6mm bolts.
Remove the dowel pins.
Remove cam chain tensioner.
Remove the cylinder head.

Remove the rocker arm shaft.

Remove the rocker arms.

HOLDER

BOLT

5. CYLINDER HEAD/ VALVE

5-5

CAMSHAFT INSPECTION

Inspect the cams of the camshaft for wear.
Service limit:
Inlet: 31.25mm
Exhaust: 30.87mm

ROCKER ARM INSPECTION

Inspect the rocker arm I.D. and the rocker arm for

wear, damage or clogged oil holes.
Rocker arm I.D.
Service limit: φ10.1mm

ROCKER ARM SHAFT INSPECTION

Inspect rocker arm shaft for wear or damage.

Rocker arm shaft O.D.

Service limit :φ10.9mm

5.INSPECTION/ADJUSTMENT

5-6

CYLINDER HEAD DISASSEMBIY

Remove carbon deposits from the combustion
chamber. Remove valve spring and valve spring and
valve with a valve spring compressor.

CYLINDER HEAD INSPECTION

Remove gasket from cylinder head with a scraper.
Check the cylinder head for crack.
Check the cylinder head for warpage with a straight
edge and a feeler gauge.
Service limit: 0.10mm

VALVE SPRING INSPECTION

Measure the free length of the inner and outer valve
spring.
Service limit:
Outer: 35mm

Inner : 28mm

5. CYLINDER HEAD/ VALVE

5-7

VALVE/VALVE GUIDE

INSPECTION

Inspect valves for scratches, burning or wear.
Check the valve movement in the guide.
Measure the valve stem O.D.
Service limit:
Intake: ∮5.42mm
Exhaust:∮5.40mm

NOTE:

Guide I.D. service limit

Intake: ∮5.50mm

Exhaust : ∮5.50mm

Measure the valve guide I.D. and calculate the stem to
guide clearance.
Service limit:
Intake: 0.08mm
Exhaust: 0.10mm
If the stem to guide clearance exceeds the service
limit, replace the valve or guide to fit.

NOTE:

Remove any carbon buildup before checking the valve
guide I.D.

The guide must be reamed when replacing a new one.

5.INSPECTION/ADJUSTMENT

5-8

VALVE GUIDE
REPLACEMENT

Drive out the valve guide from the combustion
chamber side with a 5mm valve guide remover.

NOTE:

When driving out the valve guide, do not damage the
cylinder head.

Install the new valve guide from the top of the cylinder
head, and ream it with a reamer, then clean the
cylinder head.

5. CYLINDER HEAD/ VALVE

5-9

VALVE SEAT INSPECTION/ REFACING

Clean intake and exhaust valves to remove carbon
deposits.
Apply a light coating of prussian blue to each valve
face.
Insert each valve into the guide and rotate them two
cycles.

Remove the valve and inspect the face.

CAUTION:

If the valve face is burned or damaged or unevenly,
replace the valve.

Inspect the valve seat.
If the seat is too wide or too narrow, the seat must be
refinished.

VALVE SEAT

CONTACT AREA

SERVICE LIMIT

1.5mm

SERVICE LIMIT

1.8mm

5.INSPECTION/ADJUSTMENT

5-10

VALVE SEAT GRINDING

NOTE:

Follow the instructions described in the cutter
instruction manual.

Remove any roughness from the seat by applying 4~5
kg pressure, turning the cutter left and right.

NOTE:

Add engine oil to the face when operating.

Using a 45 degree cutter,remove any roughness from
the seat.

4~5kg

CUTTER HOLDER

TURN RIGHT AND LEFT

CUTTER

ROUGHNESS

VALVE SEAT

45°

45°

32°

60°

5. CYLINDER HEAD/ VALVE

5-11

Using a 32 degree cutter, remove 1/4 of the existing
valve seat material.

Remove the bottom 1/4 of the old seat by using a 60
degree cutter.

Finish the seat to the proper width by using a 45
degree cutter.

32

o

CUTTER

VALVE SEAT

60

o

CUTTER

45

o

CUTTER

5.INSPECTION/ADJUSTMENT

5-12

If the contact area is too high on the valve,the seat
must be lowered using a 37.5 degree cutter, then finish
with a 45 degree cutter.

If the contact area is too low on the valve,the seat must
be raised using a 63.5 degree cutter, then finish with a
45 degree cutter.

After cutting the seat, apply lapping compound to the
valve face, and lap the valve using light pressure.

CONTACT AREA
TOO HIGH

CUT TOP END

CUT BOTTOM END

CONTACT AREA TOO LOW

63.5

o

5. CYLINDER HEAD/ VALVE

5-13

CYLINDER HEAD ASSEMBLY

Compress the valve springs with a valve spring
compressor and install the valve cotters into the valve
retainer.

CAUTION:

Do not compress the valve spring more than
necessary.

NOTE:

Install a new valve stem seal when assembling.

Lubricate each valve stem with the engine oil then
insert them into the guides.
Install the valve spring and retainers.

NOTE:

Install the valve springs with the tightly wound coils
facing the cylinder head.

Tap the valve stems gently with a plastic hammer to
firmly seat the cotters.

5.INSPECTION/ADJUSTMENT

5-14

CYLINDER HEAD INSTALLATION

CAMSHAFT AND CAMSPROCKET
ASSEMBLY
NOTE:

Rocker arms must be installed at the right position.

Clean the cylinder head gasket surface of any gasket
material.
Install the new gasket, O-ring and dowel pins and
chain guide.

NOTE:

Do not allow dust and dirt to enter the cylinder.

Install the cylinder head.

NOTE:

Support the cam chain to keep it from falling into the
crankcase.

Install the cam chain tensioner set and bolt and
washer.
Install dowel pins.

CAMSHAFT COMP

dowel pin

dowel pin

5. CYLINDER HEAD/ VALVE

5-15

CAM SPROCKET

INSTALLATION

Rotate the generator rotor and align the "T" mark with
the index mark.
Install the camshaft comp.
When intalling camshaft set, please take care that.The
line on the camsprocket should be in parallel with the
surface of cylinder head.(The IN/EX cam should be
faced down).
Install the camshaft holder.
Install the cylinder head nuts.

TORQUE:280 ~ 300 kgf·cm
CAUTION:

The cap nut of the four holder nuts must be installed
at the left-front side.

Install the 6mm bolts.

Install the cam chain chain tensioner.
Install the auto-tensioner. (Lock the spring cap bolt
first.)
Release the auto-tensioner lock bolt.
Adjust the valve clearance.(2-7)

Install the cylinder head cover.
Install the R/L cylinder head side cover.
Install the 6mm special bolts.

NOTE:

If the cylinder head side cover gasket is damaged or
broken, replace with a new one.

nut

nu

t

cylinder head cover

6. CYLINDER/PISTON

6-1

TROUBLE SHOOTING.......................6-1

SERVICE INFORMATION..................6-2

CYLINDER REMOVAL.......................6-3

PISTON REMOVAL.........................6-4

PISTON/PISTON RING INSPECTION

......6-5

PISTON RING INSTALLATION.....6-7

PISTON INSTALLATION.................6-9

CYLINDER INSTALLATION...............6-10

TROUBLE SHOOTING

LOW COMPRESSION

1. Worn cylinder or piston rings.

EXCESSIVE SMOKE

1. Worn cylinder,piston or piston rings.

2. Improper installation of piston rings.

3. Scored or scratched piston or cylinder wall.

OVERHEATING

1. Excessive carbon build-up on piston or
combustion chamber wall.

KNOCKING OR ABNORMAL NOISE

1. Worn piston or cylinder.

2. Excessive carbon build-up

6.CYLINDER/PISTON

6-2

SERVICE INFORNATION

GENERAL STRUCTIONS

NCA250

ITEM

STANDARD CERVICE LIMIT
Cylinder I.D. 53.005～53.015mm 53.015mm
Runout 0.05mm

Cylinder

Taper 0.05mm
Top 0.025～0.055mm 0.13mm

Piston ring to
ring groove
clearance

Second 0.015～0.040mm 0.12mm
Top 0.10～0.25mm 0.5mm
Second 0.25～0.40mm 0.5mm

Piston ring
End gap

Oil ring 0.20～0.70mm

Piston O.D. 52.55～52.60mm 52.55mm
Piston pin bore

15.002～15.008mm

15.05mm

Connecting rod small end I.D.

15.016～15.034mm

15.07mm

Piston pin O.D.

14.994～15.000mm

14.85mm

Top

0.97～0.99mm

1.460mm

Piston ring
thickness

Second

0.97～0.99mm

1.460mm

Piston
rings
groove
clearance

Cylinder to piston clearnace

0.005～0.015mm

0.11mm

6. CYLINDER/PISTON

6-3

CYLINDER REMOVAL

Remove the cylinder head.
Remove the dowel pins and gasket.
Remove the cam chain guide.
Remove the cylinder.

NOTE:

Avoid the chain falling into the crankcase during
removing the cylinder.

Remove the dowel pins and gasket.

Clean the cylinder gasket surface of any gasket
material.

NOTE:

Avoid damaging the cylinder gasket surface during
this operation.

CAM CHAIN

CAM CHAIN GUIDE

DOWEL PIN

6.CYLINDER/PISTON

6-4

CYLINDER INSPECTION

Inspect the cylinder bore for wear or damage.
Measure the cylinder I.D.

NOTE:

According to the right picture measure the cylinder
runout.

Service limit:

ITEM NCA250
Runout 0.05mm
Taper 0.05mm
I.D. 53.015mm

PISTON REMOVAL

Remove the piston pin clip with pliers.
Press the piston pin out of piston, remove the piston.

NOTE:

Avoid the clip falling into the crankcase.

TOP

MIDDLE
BOTTOM

6. CYLINDER/PISTON

6-5

PISTON / PISTON RING

INSPECTION

Measure the piston ring-to-ring groove clearance.
Service limit .
Top ring: 0.13mm
Second ring: 0.12mm

Remove the piston rings.
Inspect the piston for damage or cracks.
Inspect the piston groove for wear.

Insert each piston ring into the cylinder and measure
the ring end gap.
Top / Second ring : -0.5mm

6.CYLINDER/PISTON

6-6

Measure the piston O.D. at the skirt.
Service limit: 52.55mm

NOTE:

Measure the piston O.D. at a point from the bottom.

Calculate the piston-to-cylinder clearance.
Service limit:0.11mm

Measure the piston pin bore I.D.
Service limit:15.07mm

Measure the piston pin O.D.
Service limit:14.85mm

6. CYLINDER/PISTON

6-7

Measure the top/second ring thickness.
Service limit: 1.460mm

PISTON RING

INSTALLATION

Install the piston rings.

NOTE:

Space the piston ring end gaps 120 degree apart.

 Avoid piston and piston ring damage during

installation.

 All rings should be installed with the markings

facing up.

 After installation, the piston rings should be free

to rotate in the grooves.

TOP RING

SECOND
RING

OIL RING

6.CYLINDER/PISTON

6-8

TOP RING

SECOND RING

OIL RING

6. CYLINDER/PISTON

6-9

PISTON INSTALLATION

Install the piston, piston pin and piston pin clip.

NOTE:

 Position the "IN" mark on the piston to the

carburetor side.

 Do not let the piston pin clip fall into the crankcase.

NOTE:

 Use new piston pin clip whenever disassembling.
 Do not align the piston pin clip end gap with the

piston cutout.

END GAP

PISTON PIN CLIP

CUTOUT

6.CYLINDER/PISTON

6-10

CYLINDER INSTALLATION

Install the cylinder gasket and dowel pins.
Clean the cylinder gasket surface of any gasket
material.

NOTE:

Avoid damaging the cylinder gasket surface during
this operation.

Install the cylinder.

NOTE:

Avoid piston and piston rings damage during
installation.

Install the cam chain guide plate.
Install the cylinder gasket and dowel pins.
Install the cylinder head.(5-14)

NOTE:

Coat the cylinder and piston with the engine oil before
installing the cylinder.

CAM CHAIN

CAM CHAIN GUIDE

DOWEL PIN

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-1

TROUBLE SHOOTING.......................7-1

SERVICE INFORMATION..................7-2

RIGHT CRANKCASE COVER REMOVAL .7-3

CLUTCH.............................................7-3

OIL PUMP ..........................................7-7

GEARSHIFT LINKAGE ......................7-10

RIGHT CRANKCASE INSTALLATION......7-12

TROUBLE SHOOTING

Faulty clutch operation can be corrected by adjusting
the clutch lever free play.

CLUTCH SPINS WHEN ACCELERATING

1. No free play

2. Discs worn

3. Spring weak

CLUTCH DISENGAGED ( MOTORCYCLE CREEPS )

1. Too much free play

2. Plates warped

EXCESSIVE LEVER PRESSURE

1. Clutch cable kicked, damaged or dirty

2. Lifter mechanism damaged

HARD SHIFTING

1. Stopper plate bent

2. Improper clutch adjustment

GEARSHIFT PEDAL WON'T RETURN

1. Return spring broken or weak

2. Shift spindle bent

JUMPS OUT OF GEAR

1. Stopper arm spring broken

LOW OIL PRESSURE

1. Oil pump drive gear worn

2. Faulty oil pump

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-2

SERVICE INFORMATION

GENERAL INSTRUCTION

This section covers removal, installation and servicing
of the clutch, oil pump, filter and gearshift linkage. All
these operations can be accomplished with the engine
in the frame.

COMMON TOOLS

22mm wrench socket
Air wrench

TORQUE VALUES

Right crankcase cover 80 ~ 120 kgf·cm
Clutch lock nut 16mm 500 ~ 600 kgf

·cm

Step bar 180 ~ 200 kgf

·cm

SPECIFICATIONS

ITEM STANDARD SERVICE LIMIT

Leve
Free play

10~20mm ------------

Spring free length 30.6mm 27.9mm

Friction plate thickness 3.0mm 2.5mm

Clutch

Clutch plate warpage ------- 0.2mm

Tip clearance 0.30mm 0.35mm

Rotor-to-body clearance 0.30~0.36mm 0.40mm

Oil pump

End clearance 0~0.06mm 0.11mm

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-3

RIGHT CRANKCASE COVER
REMOVAL

Drain oil from the engine.
Disconnect the clutch cable.
Remove the right crankcase cover.

CLUTCH

CLUTCH REMOVAL

Remove the clutch bearing.

Remove the 16mm lock nut with the wrench socket
and air wrench.
Remove the clutch and drive gear.

BEARING

LOCK NUT

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-4

Remove the clutch center, friction disc.
clutch plate and pressure plate.

CLUTCH FRICTION DISC
INSPECTION

Measure the friction discs, replacing them if they are
discolored or worn.
Service limit: 2.5mm

CLUTCH CENTER

CLUTCH OUTER

CLUTCH PLATE

CLUTCH PRESSURE PLATE

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-5

CLUTCH PLATE INSPECTION

Check the plates for warpage on a surface plate using
a feeler gauge.
Service limit: 0.2mm

CLUTCH SPRING INSPECTION

Measure the clutch springs free length.
Service limit: 27.9mm

CLUTCH OUTER INSPECTION

Check the clutch outer for cracks or indentation.

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-6

CLUTCH OUTER INSTALLATION

Install the clutch outer, 20mm washer.

NOTE:

When installing the washer, it should fit with the main
shaft groove.

Install the clutch pressure plate, friction discs, clutch
plates and clutch center.

Install and tighten the 16mm lock nut.

TORQUE: 500～600 kgf·cm

WASHER

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-7

Install the clutch springs, lifter plate and tighten the
bolts.
Install the bearing.

NOTE:

Tighten the bolts in a crisscross pattern in two or
three steps.

TORQUE :500-700 kgf·cm

Install the dowel pins and gasket.
Install the right crankcase cover.
Connect the clutch cable.
Fill the crankcase with the recommended oil.
Adjust the clutch lever free play (2-14) .

OIL PUMP

OIL PUMP REMOVAL

Remove the right crankcase cover (7-3).

BEARING

OIL PUMP

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-8

Remove the 6mm screws, remove the oil
pump.

OIL PUMP DISASSEMBLY

Remove the oil pump drive gear.
Remove the oil pump drive gear and oil
pump plate.

OIL PUMP INSPECTION

Measure the inner-to-outer rotor clearance
of the oil pump.
Service limit: 0.35mm

6mm screws

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-9

Measure the outer rotor to oil pump body clearance.
Service limit: 0.40mm

Measure the oil pump upper clearance.
Service limit: 0.11mm

OIL PUMP ASSEMBLY

Install the inner and outer rotors into the oil pump body.
Install the oil pump drive shaft.
Install the oil pump drive gear.
Install the oil pump cover.

NOTE:

Align the cutout in inner rotor with the cutout on the
shaft.

DRIVE SHAFT

OIL PUMP COVER

DRIVE GEAR

OIL PUMP BODY

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-10

Check the oil pump for rotating freely.

OIL PUMP INSTALLATION

Install a O-rings.
Install the oil pump to the right crankcase.

GEARSHIFT LINKAGE

GEARSHIFT LINKAGE DISASSEMBLY

Remove the clutch (7-3).
Remove the gearshift pedal.
Remove the gearshift spindle.

O-RING

OIL PUMP

GEARSHIFT SPINDLE

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-11

Remove the gearshift drum stopper.
Remove the gearshift cam.
Check each part for wear or damage.

GEARSHIFT LINKAGE ASSEMBLY

Install the four 10mm rollers.
Align the hole of the gearshift cam with the roller, then
install the gearshift cam.

Install the gearshift drum stopper.

NOTE

After installation, check the drum stopper
operation.

GEARSHIFT CAM

GEARSHIFT DRUM
STOPPER

ROLLER

GEARSHIFT CAM

GEARSHIFT DRUM STOPPER

7.CLUTCH/OIL PUMP/GEAR SHIFT

7-12

Install the gearshift spindle.

NOTE :

Hook the gearshift return spring on the
crankcase abutment.

Install the clutch.
Install the primary drive gear.
Install the oil pump drive gear.
Install the drive gear.
Install the oil through pin.
Install the oil pump.

RIGHT CRANKCASE COVER
INSTALLATION

Install the right crankcase cover.
Connect the clutch cable.
Fill the crankcase with recommended oil.
Adjust the clutch free play.

OIL PUMP

CLUTCH

DRIVE GEAR

8. A.C.GENERATOR

8-1

TROUBLE SHOOTING ......................8-1

LEFT CRANKCASE COVER REMOVAL...........8-2

GENERATOR ROTOR REMOVAL....8-2

GENERATOR ROTOR INSTALLATION............8-3

LEFT CRANKCASE COVER INSTALLATION ....8-4

STARTER MOTOR REMOVAL .........8-4

STARTER MOTOR GEAR SET.........8-5

8. A.C.GENERATOR

8-2

LEFT CRANKCASE COVER
REMOVAL

Remove the gearshift pedal.
Remove the left crankcase rear cover.

NOTE:

Generator stator is in the left crankcase cover, it can
be removed by removing the attaching screws.

GENERATOR ROTOR REMOVAL

Remove the left crankcase cover.
Remove the rotor bolt.

Remove the generator rotor.
Remove the generator stator.

ROTOR SETTING BOLT

8. A.C.GENERATOR

8-3

STATOR INSPECTION

Check the stator for continuity.

GENERATOR ROTOR
INSTALLATION

Reverse the procedure of removal to assembly.

NOTE :

 Check wire for security in its place.

 Do not interfere the wire with the rotor.

Install and tighten the rotor.

TORQUE: 400~500 kgf··cm

8. A.C.GENERATOR

8-4

LEFT CRANKCASE
COVER INSTALLATION

Install the left crankcase cover (with stator coil)
Connect the generator wire connectors.
Route the neutral switch wire through the groove in the
left crankcase cover.
Install the left crankcase rear cover.
Install the gearshift pedal.

STARTER MOTOR
REMOVAL

Disconnect the starter motor wire connector.
Remove the starter motor attaching bolts.
Remove the starter motor.

STARTER DRIVEN GEAR REMOVAL

Remove the left crankcase cover (8-2).
Remove the generator rotor. (8-2)
Remove the starter driven gear.

ELECTRIC
CONNECTOR

BOLTS

STARTER
DRIVEN GEAR

8. A.C.GENERATOR

8-5

STARTER MOTOR GEAR SET

1. Starter driven gear

2. Washer

3. Starter reduce gear

4. Starter motor

1

2

3

4

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-1

TROUBLE SHOOTING.......................9-1

SERVICE INFORMATION..................9-2

CRANKCASE SEPARATION .............9-3

CRANKSHAFT REMOVAL.................9-4

TRANSMISSION DISASSEMBLY......9-6

TRANSMISSION ASSEMBLY............9-9

CRANKSHAFT INSTALLATION.........9-11

CRANKCASE ASSEMBLY.................9-11

TROUBLE SHOOTING

HARD TO SHIFT

1. Shift fork bent

2. Shift fork shaft bent

TRANSMISSION JUMPS OUT OF GEAR

1. Gear dogs worn

2. Shift fork bent or damaged

3. Shift fork shaft bent

CRANKSHAFT NOISE

1. Worn connecting rod big end bearing

2. Bent connecting rod

3. Worn crankshaft bearing

GEAR NOISE

1. Worn transmission gears

2. Worn spline shafts

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-2

SERVICE INFORMATION

GENERAL INSTRUCTION

Transmission and crankshaft repairs require crankcase separation.
Remove the following parts before separating the crankcase:
Engine removal 4-2
Cam shaft removal 5-2
Cylinder / Piston removal 6-3
Clutch / oil pump / Gearshift linkage removal 7-3
Left crankcase cover removal 8-2

SPECIAL TOOLS

Bearing driver
Bearing driver pilot

SPECIFICATIONS

ITEM STANDARD SERVICE LIMIT

I.D. 12.000～12.018mm 12.02mm

Gearshift fork

Claw thickness 4.925～5.000mm 4.8mm

Shift fork shaft O.D. 11.976～11.994mm 11.9mm

Runout 0.01mm
Connecting rod small End I.D. 15.016～15.034mm 15.08mm

Axial 0.10～0.35mm 0.6mm

Crankshaft

Connecting rod big
End side clearance

radial 0.004～0.012mm 0.05mm

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-3

CRANKCASE SEPARATION

Remove the right crankcover and interial parts.
(7-3~ 7-13)

Remove left cover and interial parts.

Remove the left crankcover all 6mm attaching bolts.
Separate the left crankcase from the right crankcase.
Remove the gasket and dowel pins.

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-4

CRANKSHAFT REMOVAL

Remove the left crankcase.
Remove the crankshaft.

CRANKSHAFT INSPECTION

Measure the connecting rod big end side clearance
with a feeler gauge.
Service limit: 0.60mm

Follow the arrow indicated direction to measure the
connecting rod big end radial clearance.
Service limit:0.05mm

CRANKCASE

CRANKCASE

FEELER GAUGE

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-5

Place the crankshaft on a V-block and measure the
runout using a gauge.

NOTE:

Coat the bearing and connecting rod big end with
engine oil before installation.

Runout
Service limit: 0.01mm

Measure the connecting rod small end I.D.
Connecting rod small end I.D.
Service limit: ∮15.08mm

CRANKSHAFT BEARING
INSPECTION

Spin the crankshaft bearing by hand and check for
play. The bearing must be replaced if it is noisy or has
excessive play.

FREE PLAY

FREE PLAY

A

XIAL

RADIAL

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-6

TRANSMISSION
DISASSEMBLY

Remove the crankshaft.
Remove the shift fork shaft.
Remove the shift drum.
Remove the shift forks.

SHIFT FORK AND SHIFT FORK
SHAFT INSPECTION

Check the shift fork for wear, bending or damage.
Measure the shift fork I.D.
Service limit: 12.02mm

Measure each shift fork claw thickness.
Service limit: 4.80mm

MAIN SHAFT

COUNTER

SHAFT

SHIFT DRUM

CHECK FOR WEAR
OR DAMAGE

SHIFT FORK

SHAFT

SHIFT FORK

SHIFT DRUM

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-7

Measure the shift fork shaft O.D.
Service limit: 11.976mm

SHIFT DRUM INSPECTION

Check the gearshift drum for wear or damage.

Disassemble the transmission gears.
Check each gear for wear or damage and replace if
necessary.

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-8

Check the crankcase oil orifice for clogged, blowing
through with compressing air if necessary.

Check the crankcase bearings, replace them if they
have excessive free play or noisy.

BEARING INSTALLATION

Install the bearings into the left, right crankcase with
special tools.

NOTE:

Install the bearing horizontally, to prevent bearing
damage.

FREE PLAY

FREE PLAY

A

XIAL

RADIAL

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-9

TRANSMISSION ASSEMBLY

NOTE:

Before assembling,coat each gears with engine oil.

Assemble the gears of the countershaft and mainshaft.

NOTE:

Seat the snap ring in the ring groove properly.

Counter shaft

Main shaft

C1

C3

C4

C5C5

Driver sprocke

t

C2

M2

M5

M4

M3

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-10

Install the oil plate comp in the right crankcase.

Install the crankshaft assemblies in the right
crankcase.

Install the mainshaft and countershaft
assemblies in the right crankcase.

NOTE:

Keep the thrust washers in place during installation.

Install the mainshaft, countershaft and shift forks.

OIL PLATE

CRANKSHAFT

MAINSHAFT

COUNTERSHAFT

SHIFT FORK

9.CRANKSHAFT/CRANKCASE/TRANSMISSION

9-11

Install the gearshift drum.
Install the shift fork shaft.

NOTE:

Engage the shift fork guide pin with the drum
groove by raising the shift fork.

After assembling, check each part for moving
freely.

CRANK CASE ASSEMBLY

Install the gasket and dowel pins.
Install the left crankcase on the right crankcase.

NOTE:

Make sure that the gasket is in place.

SHIFT FORK SHAFT

GEARSHIFT DRUM

10. CARBURETOR

10-1

TROUBLE SHOOTING.......................10-2

SERVICE INFORMATION..................10-2

CARBURETOR REMOVAL................10-3

THROTTLE VALVE DISASSEMBLY..10-3

FLOAT/FLOAT VALVE/JETS DISASSEMBLY 10-4

FLOAT/FLOAT VALVE/JETS ASSEMBLY....10-6

FLOAT/LEVEL ADJUSTMENT...........10-6

THROTTLE VALVE ASSEMBLY........10-6

CARBURETOR INSTALLATION........10-7

10. CARBURETOR

10-2

TROUBLE SHOOTING

ENGINE CRANKS BUT NOT START

1. No fuel in the fuel tank

2. No fuel in the carburetor

3. Too much fuel in the combustion chamber

4. No spark at the spark plug ( ignition malfunction )

5. Air cleaner clogged

ENGINE IDLE ROUGHLY

1. Idling speed incorrect

2. Ignition malfunction

3. Low compression

4. Rich mixture

5. Lean mixture

6. Air cleaner clogged

7. Air leaking into intake pipe

8. Fuel contaminated

LEAN MIXTURE

1. Carburetor jets clogged

2. Float chamber vent clogged

3. Fuel filter clogged

4. Fuel line restricted

5. Float level too Iow

6. Float valve faulty

RICH MIXTURE

1. Choke stuck closed

2. Float valve faulty

3. Float level too high

SERVICE INFORMATION

GENERAL INSTRUCTIONS

Take cautions when dealing this operation.
Always work in a well-ventilated area and away from
sparks or open flames. When assembling, note the
locations of the jets and place them individually.

SPECIAL TOOL

Float gauge

10. CARBURETOR

10-3

CARBURETOR REMOVAL

Disconnect the fuel line.
Disconnect the all connect tubes.
Drain fuel from the carburetor.

WARNING:

Keep away from flames or sparks. Wipe up spilled
gasoline at once.

Loosen the carburetor band.

THROTTLE VALVE
DISASSEMBLY

Disconnect the throttle cable.

CARBURETOR

BAND

CARBURETOR
PROTECT
COVER

BAND

THROTTLE CABLE

10. CARBURETOR

10-4

Remove the carburetor assembly.

VACUUM CHAMBER
DISASSEMBLE

Remove the two screws and remove the vacuum
chamber cover.
Remove the piston spring.
Remove the needle holder, jet needle spring, jet
needle and vacuum piston.

WARNING:

Avoid damage to the vacuum membrane.

INSPECTION

Inspect the jet needle for wear or damage.
Inspect the vacuum piston for damage.
Inspect the vacuum membrane for damage.

ASSEMBLY

Install the vacuum piston ,vacuum membrane, jet
needle, needle holder, piston spring on the carburetor
body.

NOTE:

Avoid damage to the vacuum membrane.

vacuum piston

j

et needle spring

j

et needle

acuum chambe

r

cover

Piston spring

Needle holder

vacuum

membrane

10. CARBURETOR

10-5

FLOAT/FLOAT VALVE/JETS
DISASSEMBLE

Remove the float chamber body.

WARNING:

Pour the float chamber gasoline into the tank.

Pull out the float pin, remove the float and float valve.

FLOAT VALVE INSPECTION

Inspect the float valve surface for wear or damage.

float chamber

float valve

float pin

float

WEAR OR DAMAGE

10. CARBURETOR

10-6

Remove the main jet, main jet holder and slow jet.
NOTE:

Avoid damage to the jets.

Remove the air screw.

NOTE:

Before removing air screw, record the number of
relations until it rests lightly,so it can be returned to its
original position.

Check each part for damage.
Blow open all body openings with compressed air.

main jet

main jet

slow jet

main jet holder

air screw

10. CARBURETOR

10-7

FLOAT/FLOAT VALVE/JETS
ASSEMBLY

Install the stop screw, the main jet, main jet holder and
slow jet.

NOTE:

Do not damage jets at the time of assembly.

FLOAT LEVEL ADJUSTMENT

If the float level is too high or too low,bend the float arm
for adjusting.
Float level: 24mm

24mm

10. CARBURETOR

10-8

Connect the throttle cable.

NOTE:

 Make sure that the throttle cable is pulled tightly.

CARBURETOR
INSTALLATION

Reverse the procedure of removal to install
the carburetor.
Then adjust the followings:
Throttle grip free play (2-10).
Idling speed (2-11).

throttle cable

14. IGNITION SYSTEM

14-1

TROUBLE SHOOTING.......................14-1

SERVICE INFORMATION..................14-2

IGNITION COIL..................................14-3

TROUBLE SHOOTING

ENGINE CRANKS BUT NOT START

1. No sparks at the spark plug

2. Improper ignition timing

3. Faulty plug

NO SPARKS AT THE SPARK PLUG

1. No current in primary circuit

2. High tension cord broken

3. Faulty ignition coil

4. Faulty A.C. generator

5. Faulty C.D.I. unit

ENGINE RUNS BUT ROUGHLY

1. Primary circuit

-- C.D.I. unit failure

-- Faulty A.C. generator

-- Faulty ignition coil

-- Loose wires

-- Poorly contacted switch terminals

2. Secondary circuit

-- Faulty,spark plug

-- Faulty high tension cord

-- Faulty ignition coil

3. Ignition timing

-- Faulty A.C. generator

-- Faulty C.D.I. unit

C.D.I.

Black/white

Black/red

Black/yellow

Green

Blue/yellow

14. IGNITION SYSTEM

14-2

SERVICE INFORMATION

GENERAL INSTRUCTION

This section contains the ignition system.
Be sure that the battery is fully charged before
diagnosing troubles in the ignition system.
Also refer to the following pages:
Spark plug 2-5
Ignition timing adjustment 2-8

SPECIFICATIONS

Spark plug: A6RTC
Spark plug gap: 0.6~0.7mm(0.024-0.028in)
Ignition timing : 15°±2°/1500rpm

29.5°±2° /4000rpm

14. IGNITION SYSTEM

14-3

IGNITION COIL

IGNITION COIL REMOVAL

Remove the seat.
Remove the fuel tank.
Disconnect all wires to the ignition coil.
Remove the ignition coil.

IGNITION COIL TEST

Check the ignition coil output using a tripolar tester.

NOTE:

Follow the instructions described in the user
manual.

Check the primary circuit, it is normal if there is
conductivity when connecting a ohmmeter.

PRIMARY COIL 0.31±0.03KΩ

SECONDARY COIL 4.0±0.4KΩ

IGNITION COIL