E-TON VIPER 50 ST, YUKON ST Service Manual

SER VICE MANUAL

CONTENTS

1. INFORMATION

2. MAINTENANCE

3. ENGINE REMOVAL AND INSTALLATION

4. ENGINE FUEL SYSTEM

5. ENGINE LUBRICATION AND COOLING SYSTEM

6. ENGINE COMBUSTION SYSTEM

7. TRANSMISSION SYSTEM

8. STEERING SYSTEM

9. FRONT WHEEL SYSTEM

10. REAR WHEEL SYSTEM

11. FENDERS AND EXHAUST PIPE

12. ELECTRICAL SYSTEM

13. TROUBLE SHOOTING

1. INFORMATION

1.1 SAFTY

1.2 NOTES

1.3 SPECIFICATION

1.4 SERIAL NUMBER

1.5 TORQUE VALUE

1.1 SAFETY

GASOLINE

Gasoline is extremely flammable and is explosive under certain condition.

Do not smoke or allow sparks or flames in your work area.

●

CARBON MONOXIDE

Never run the engine in a closed area. The exhaust contains poisonous carbon

monoxide gas that may cause loss of consciousness and lead to death.

●

BATTERY ELECTROLYTE

The battery electrolyte contains sulfuric acid. Protect your eyes, skin and

clothing. If you contact it, flush thoroughly with water and call a doctor if electrolyte

gets in your eyes.

● HOT PARTS

Engine and exhaust pipe become very hot and remain hot for one hour after the

engine is run. Wear insulated gloves before handling these parts.

● USED ENGINE/GEAR OIL

Used engine oil and gear oil may cause skin disease if repeatedly contact with

the skin for long periods.

Keep out of reach of children.

1.2 NOTES

All information, illustrations, directions and specifications included in this publication are base on the latest

product information available at the time of approval for printing.

JI-EE Dynamic Technology Industry Co., Ltd. reserves the right to make changes at any time without notice

and without incurring any obligation whatever.

No part of this publication may be reproduced without written permission.

2

1.3 SPECIFICATION ENGINE

(for Viper

ST

&Yukon

ST

in this service manual)

COLORING

Specifications subject to change without notice.

3

Viper

ST

EXL-50 Yukon

ST

EXL-50

SUSPENSION
Front

Single A-arm / Adjustable Shocks

Rear

Swing Arm / Adjustable Shock
BRAKES
Front

Dual Mechanical drum

Rear

Hydraulic Disc
TIRES
Front

20/6-10

Rear 20/10-9
PRESSURE 【psi (0.23 kgf/cm

2

)】

Front

12(0.8) 12(0.8)

Rear

12(0.8) 12(0.8)

Vip

er

EXL-50

Yukon

EXL-50

CHASSIS
Overall Length 1670 mm 1750 mm
Overall Width 940 mm 1010 mm
Overall Height 1040 mm 1065 mm
Seat Height 760 mm 760 mm
Wheel base 1110 mm 1115 mm
Ground Clearance 120 mm 120 mm
Dry Weight 152 kg 152 kg
Fuel T ank Capacity 4.5 Liters 4.5 Liters

Type Two cycle air cooled
Displacement 49.3 c.c.
Bore and Stroke

40.0

X

39.2mm

Compression ratio 6.8:1
Maximum Torque (Nm/rpm)

4.5 Nm/6000

r

p

m

Carburetor Piston type
Ignition Capacitor Discharge
Starting Electric and kick starter
Lubrication Forced pressure and wet sump
Transmission Automatic (C.V.T. V-belt) Fr Neut .Rev

Maximum P ower (ps/rpm)

3.8 ps/6000rpm

1.4 SERIAL NUMBER
(For Viper

ST

EXL-50 / YukonST EXL-50 in this service manual)

The frame serial number is stamped on the front of the frame.

The engine serial number is stamped on the left side of the crankcase.

Frame serial number

Engine serial number

4

.5 TORQUE VALUES

(For EXL 50 in this service manual)

STANDARD

● 5 mm bolt and nut

5 N.m (3.5 lbf.ft)

● 6 mm bolt and nut

10 N.m (7.2 lbf.ft)

● 8 mm bolt and nut

22 N.m (16 lbf.ft)

●10 mm bolt and nut

35 N.m (25 lbf.ft)

●12 mm bolt and nut

55 N.m (40 lbf.ft)

ENGINE

● Cylinder head nut

28 N.m (20.7 lbf.ft)

● Spark plug

12 N.m (8.9 lbf.ft)

● Cylinder head bolt

20 N.m (14.8 lbf.ft)

● Alternator bolt

8 N.m (5.9 lbf.ft)

FRAME

● Handlebar upper holder bolt

24 N.m (17.7 lbf.ft)

● Throttle housing cover screw

4 N.m (2.9 lbf.ft)

● Steering shaft nut

50 N.m (36.9 lbf.ft)

● Steering shaft holder bolt

33 N.m (24 lbf.ft)

● Wheel rim bolt

18 N.m (13.3 lbf.ft)

● Tie rod lock nut

35 N.m (25.8 lbf.ft)

● King pin nut

40 N.m (29 lbf.ft)

● Handlebar lower holder nut

40 N.m (29.5 lbf.ft)

● Front wheel bolt

24 N.m (17.7 lbf.ft)

● Front axle castle nut

40-60 N.m (30-45 lbf.ft)

● Front brake arm nut

4 N.m (3.0 lbf.ft)

● Rear brake arm nut

7 N.m (5.2 lbf.ft)

● Rear axle castle nut

40-60 N.m (30-45 lbf.ft)

● Rear wheel bolt

24 N.m (17.7 lbf.ft)

● Exhaust muffler mounting bolt

30 N.m (22.1 lbf.ft)

● Engine hanger bolt

30 N.m ( 22 lbf.ft)

● Rear axle holder bolt

90 N.m (65 lbf.ft)

● Swing arm pivot nut

90 N.m (65 lbf.ft)

● Rear shock absorber mounting nut

45 N.m (33 lbf.ft)

5

2. MAINTENANCE

2.1 MAINTENANCE DATA 2.8 IDLE SPEED

2.2 MAINTENANCE SCHEDULE 2.9 DRIVE CHAIN

2.3 FUEL TUBE 2.10 BRAKE SYSTEM

2.4 THROTTLE OPERATION 2.11 WHEELS AND TIRES

2.5 THROTTLE CABLE ADJUSTMENT 2.12 STEERING SYSTEM

2.6 AIR CLEANER 2.13 TOE-IN

2.7 SPARK PLUG 2.14 GEAR OIL

2.1 MAINTENANCE DATA

SPECIFICATION

SPARK PLUG:

SPARK PLUG GAP: 0.6-0.7 mm
RECOMMENDED SPARK PLUGS: NGK BPR7HS
THROTTLE LEVER FREE PLAY: 5-10 mm
IDLE SPEED: 1800±100 rpm
BRAKE LEVER FREE PLAY:

15-25 mm

DRIVE CHAIN SLACK

10-25 mm
FRONT/REAR TIRE PRESSURE MIN 2 psi (12.5kpa)
TOE-IN 5±10 mm

TORQUE VALUES

SPARK PLUG 25-30 N.m
TIE-ROD LOCK NUT 35-43 N.m

ENGINE OIL JASO FC Grade or same degree oil

GEAR LUBRICATION OIL SAE 90

2.2 MAINTENANCE SCHEDULE

The maintenance internals in the follow table is based upon average riding, conditions. Riding in unusually
dusty areas, require more frequent servicing. (For ATV all serial in this service manual)

INITIAL SERVICE

(

First week

)

REGULAR SERVICE

(Every

30 operating days

)

EVERY YEAR

FUEL LINE
THROTTLE OPERATION
AIR CLEANER
SPARK PLUG
CARBURETOR IDLE SPEED
DRIVE CHAIN
BRAKE SHOE WEAR
BRAKE SYSTEM
NUT, BOLT, FASTENER
WHEEL
STEERING SYSTEM
SUSPENSION SYSTEM
C.V.T. AIR FILTER
GEAR OIL
REVERSE GEAR OIL-RXL90R

I

I

I, L

I
I
I

I

C

I
I

I, L

I
I
I

C

I

I

I
I

R
R

Note – I: Inspect and Clean, Adjust, Lubricate or Replace, if necessary

C: Clean L: Lubricate R: Replace

2.3 FUEL TUBE

Inspect the fuel lines for deterioration, damage or
leakage and replace if necessary.

2.4 THROTTLE OPERATION

Inspect for smooth throttle lever full opening and
automatic full closing in all steering positions.
Inspect if there is no deterioration, damage or kinking
in the throttle cable, replace it if necessary.
Check the throttle lever,

free play is 5-10 mm

at the tip

of the throttle lever.
Disconnect the throttle cable at the upper end.
Lubricate the cable with commercially lubricant to
prevent premature wear.

2.5 THROTTLE CABLE ADJUSTMENT

Slide the rubber cap of the adjuster off the throttle
Housing, loosen the lock nut and adjust the free play
of the throttle lever by turning the adjuster on the throttle
housing. Inspect the free play of the throttle lever.

2.6 AIR CLEANER

Unscrew the air cleaner cover screws.
Pull out the air filter element from the air cleaner case.
Wash the element in non-flammable solvent, squeeze
out the solvent thoroughly.
Let it dry.
Soak the filter element in gear oil and then squeeze
out the excess oil.
Install the element into air cleaner carefully.

2.7 SPARK PLUG

This spark plug located at the front of the engine.
Disconnect the spark plug cap and unscrew the spark plug.
Check the spark plug electrodes for wearness.
Change a new spark plug if the electrodes and insulator tip
appear unusually fouled or burned.
Discard the spark plug if there is apparent wear or if the
insulator is cracked or chipped.

The spark plug gap shall keep in 0.6-0.7mm.

With the sealing washer attached, thread the spark plug in
by hand to prevent cross threading.

Tighten the spark plug with 25-30 N.m

2.8 IDLE SPEED

Connect an engine speed meter.
Warm up the engine, 10 minutes are enough.
Turn the idle-speed adjust screw on the carburetor
to obtain the idle speed. “Turn in” (clockwise) will get higher
speed. “Turn out” (counter clockwise) will get lower speed.

IDLE SPEED: 1800±100 rpm

2.9 DRIVE CHAIN

Inspect the chain slack.

The standard is 10-25mm.

Adjust the chain slack.
Loose the lock bolts (4 pcs) then adjust the drive chain
slack by turn the adjusting nut.
Tighten the four lock bolts.

When the drive chain becomes very dirty, it should be
removed, cleaned and lubricated by specify lubricator.
Using commercial chain lubricant to lubricate the drive
chain.
Clean the drive chain with kerosene and wipe it dry.
Inspect the drive chain for possible wear or damage.
Replace the chain, if it is worn excessively or damaged.

Inspect the sprocket teeth, if it is excessive wear
or damage, replace it.

Inspect the chain-tensioned roller.
Replace it, if necessary.

2.10 BRAKE SYSTEM

Inspect the front brake lever and cable for excessive
play or other damage.
Replace or repair if necessary.
Measure the free play of the brake lever at the end of the
brake lever.

The standard of free play is 15-25 mm.

Inspect the rear brake lever and cable for excessive
play

or

other damage.
Replace or repair if necessary.
Measure the free play of the rear brake lever at the end of
the

lever.

Th

e standard is 15-25 mm.

BRAKE SHOE WEAR
FRONT

BRAKE

Release the front wheel and inspect the brake lining
thickness.

Service Limit: 2.0mm(0.08 inch)

If either lining is worn beyond the service limit, replace
Both brakes shoes.

2.11 WHEELS AND TIRES

Inspect the tire surfaces for cuts, nails or other sharp objects.
Check

the tire surfaces at cold tire condition.

The standard of tire pressure is 1.2±0.3 ps

i.

(0.8 kgf/cm2)

2.12 STEERING SYSTEM

Check the free play of the steering shaft with the front wheels,
turned

straight ahead.
When there is excessive play, inspect the tie-rod, kingpin
bushing

and ball joint.

STEERING SHAFT HOLDER BUSHING

Remove the front fender first.
Remove the steering shaft holder and check the steering

shaft bushing for wears or damage.
If the bushing is worn or damaged, change a new
one.
Grease the steering shaft bushing and install the parts in the
reverse order of removal.

Torque: steering shaft holder bolt: 33 N.m (24 lbf.ft)

2.13 TOE-IN

Let the vehicle on level ground and the front wheels facing
straight ahead.
Mark the centers of the tires to indicate the axle center
height.
Measure the distance between the marks.

Carefully move the vehicle back, let the wheels have
turned 180 °, so the marks on the tires are aligned
with the axle center height.
Measure the distance between the marks.
Calculate the difference in the front and rear
measurements.

Toe-in: 5±10mm

If the toe-in is out of standard, adjust it by changing
the length of the tie-rods equally by turning the tie-rod
while holding the ball joint.
Tighten the lock nuts.

Torque: 35-43 N.m

2.14 GEAR OIL

Gear oil needs to be changed every year.
There is a gear oil release bolt at the rear of engine.
Unscrew this release bolt and can let the dirty oil flow out.
The re-add oil hole is on the engine case beside gearbox.

3. ENGINE REMOVAL AND INSTALLATION

3.1 SERVICE INFORMATION

3.3 ENGINE INSTALLATION

3.2 ENGINE REMOVAL

3.1 ENGINE SHALL BE REMOVED IN THE CONDITIONS OF NECESSARY REPAIRMENT OR
ADJUSTMENT TO THE TRANSMISSION AND COMBUSTION SYSTEM ONLY

3.2 ENGINE REMOVAL

Remove the seat and rear fender. (Chapter 11) Remove the
spark plug cap from the spark plug. Remove the exhaust
pipe.
Disconnect the carburetor cable by unscrew two screws on
top of the carburetor.
Take off oil pump cable from the oil pump control plate. Oil
pump is under the right side of engine.

Disconnect the wire connectors. There are three
connectors for carburetor auto-choke, starter motor
and generator respectively.
Remove the drive chain cover. This is under the chain.
Remove the drive chain retaining clip and master link,
and remove the drive chain.

Remove the three engine hanger nuts and bolts.
Remove the engine from the right side of frame.

3.3 ENGINE INSTALLATION

Engine installation is essentially the reverse order of removal.

The torque of engine hanger bolt is 24-30 Nm

Route the wires and cable in reverse order properly.

★

UNPROPER

ADJUSTMENT

TO THE

POORLY

I

DLE SPEED

SCREW

★

I

GNITION MALFUNCTION

★

F

UEL/AIR MIXTURE RATIO NO GOOD

★

A

IR CLEANER DIRTY

★

I

NSULATOR LEAKS

★

F

UEL TAN K CAP BREATHING HOLE

CLOGGED

L

EAN MIXTURE

★

FUEL JET

OF

CARBURETOR CLOGGED

★

F

UEL TAN K CAP BREATHING HOLE

CLOGGED

★

F

UEL FILTER CLOGGED

★

F

UEL FLOWS IN THE

TUBE

UNSMOOTHLY

★

F

LOAT LEVEL IN CARBURETOR TOO

LOW

R

ICH MIXTURE

★

F

LOAT NEEDLE VALVE IN

CARBURETOR FAULTY

★

F

LOAT LEVEL TOO HIGH

★

A

IR DUCT IN CARBURETOR

IS

CLOGGED

★

A

IR CLEANER DIRTY

4.1 FUEL TANK

REMOVAL
Remove the seat and rear fender.
Disconnect the fuel line from the carburetor.
Remove the fuel tank cap and front fender.
Unscrew the fuel tank fixed bolts.
Note: Keep gasoline away from flames or sparks.

Wipe up spilled gasoline at once.

4.2 CARBURETOR

REMOVAL
Remove the air cleaner.
Disconnect the fuel line and auto-choke electric wire.
Unscrew the intake pipe mounting bolts at the
carburetor then removes the carburetor.
Note: Turn fuel cup on (off) position

Remove the carburetor cap.
Remove the throttle cable from the throttle valve while
depressing the throttle valve spring.

Remove the needle clip retainer, the jet needle and
needle clip. Inspect the throttle valve and
jet needle surface for wearness, scratches or dirt.

4. ENGINE FUEL SYSTEM

4.1

FUEL TANK

4.2

CARBURETOR

DISASSEMBLY

Unscrew the float chamber screws and remove
the carburetor chamber.

Disassembly the float and float needle
valve.

Inspect the seat of the float needle valve for
wear or damage.

Disassembly the slow jet, main jet, throttle adjusting
screw and air flow adjusts screw.

Inspect all the jets and scre ws for wear or damage. Clea

n

the passages and jets with compressed air.

carbureto

r

chambe

r

slowjet

main jet

throttle adjusting screw

ai

r

flow adjusts screw

ASSEMBLY

Clean all parts in solvent and blow it dry with compressed air.
Assembly is essentially the reverse order of disassembly.

THROTTLE VALVE ASSEMBLY

Install the needle clip on the jet needle.
Install the jet needle into the throttle valve.
Assembly the throttle cable, spring and the throttle valve.
Align the throttle valve groove with the idle speed adjust
screw and install the carburetor cap to the carburetor.

5.

ENGINE LUBRICATION

AND COOLING SYSTEM

5.1 ENGINE LUBRICATION SYSTEM

5.4 COOLING SYSTEM

5.2 CAUTION

5.3 OIL PUMP

5.5 TROUBLESHOOTING

5.1 ENGINE LUBRICATION SYSTEM

The engine drives the pump gears of oil pump
crankshaft. Pump gears rotate the plunger shaft in oil
pump. This shaft sent the lubricating oil into the crankcase
to mix with the mixture of air-fuel flow evenly.
The oil drops and foam cover the cylinder inner wall,
piston surface and piston rings.

5.2 CAUTION

Having enough oil supply to engine is very important.
If the oil quantity is not enough, this engine will be serious scratched, and then this engine will stop, even
cannot work again.
When this engine is serious scratched, you need to change the piston, piston rings and cylinder together.
Also you need to check the combustion system and lubrication system carefully.

5.3 OIL PUMP

The quantity of oil that deliver out from oil pump increased by the engine speed and the carburetor throttle
open width. Oil pump is under the right side of the engine and connected by a control cable of throttle.

5.4 COOLING SYSTEM

The engine-cooling fan sucks the air.
The cooling fan is on the right side of engine.
The air is forced to flow through cylinder fin and
cylinder head. So, the cylinder and piston will not
over heat.

5.5 TROUBLESHOOTING

NO ENOUGH OIL SUPPLY TO ENGINE ★ THE OIL LEVEL IN OIL TANK IS TOO LOW.

★ OIL TUBES WERE NOT FIXED WELL.
★ OIL HAS LEAKAGED FROM TUBE ENDS.
★ OIL TUBES WERE BROKEN.
★ OIL TUBES WERE CLOGGED.
★ OIL PUMP CANNOT WORK.

ALWAYS INSUFFICIENT OIL LEVEL ★ EXTERNAL OIL LEAKS
IN LUBRICATE OIL TANK ★ WORN CYLINDE HEAD GASKET

★ WORN PISTON RINGS

6. ENGINE COMBUSTION SYSTEM

11.1 TROUBLESHOOTING

11.3 CYLINDER AND PISTON INSPECTION

11.2 CYLINDER AND PISTON REMOVAL

11.4 INSTALLATION

6.1 TROUBLESHOOTING

LOW COMPRESSION ★ CYLINDER HEAD

HEAD GASKET LEAKING OR DAMAGED

WARPED OR CRACKED CYLINDER HEAD

★ CYLINDER OR PISTON RINGS WORN OUT

HIGH COMPRESSION

★

EXCESSSIVE CARBON BUILD-UP ON

PISTON

HEAD OR IN COMBUSTION CHAMBER

EXCESSIVE NOISE

★

PISTON AND CYLINDER WORN

OUT

★

EXCESSIVE CARBON BUILD-UP

EXCESS SMOKE ★ CYLINDER OR PISTON RINGS WORN OUT

★ IMPROPER INSTALLATION OF

PISTON RINGS

★ PISTON OR CYLINDER WALL SCORED OR

SCRATCHED

OVERHEATING

★ EXCESSIVE CARBON BUILD-UP ON THE

PISTON OR COMBUSTION CHAMBER

★ ENGINE COOLING SYSTEM (FAN,

CYLINDER COVER…) WORKS BADLY.

★ OIL SUPPLY IS OUT OF ORDER.

★ WRONG IGNITION TIMING

6.2 CYLINDER AND PISTON REMOVAL

Remove the seat and rear fender.
Remove the exhaust pipe.
Remove the spark plug cap.
Disconnect the wire.
Drag out the engine.
Disassembly the air cleaner and carburetor.

Remove the intake pipe mounting bolts.
Remove the cylinder bolt nuts.

Remove the cylinder head.
Remove the cylinder carefully, then you can see
the whole piston.
Remove one piston pin clip.
Remove the piston and piston pin.
Spread each piston ring and remove it by lifting up
at a point just opposite the gap.
Note: Don’t let the clip drop into engine crankcase.

6.3 CYLINDER AND PISTON INSPECTION

Inspect the cylinder bore for wear or damage.
Measure the cylinder inner diameter at three levels
in X and Y-axis.

Tape r limit: 0.10 mm
Out of round: 0.10 mm

Check the cylinder head mating surface for warp
with a straight edge and feeler gauge.

Service limit: 0.10 mm

Insert each piston ring into the cylinder, and measure
the end gap.

Service limit: 0.5 mm

Measure the clearance between ring and groove.

Service limit: 0.09 mm

Measure the piston outer diameter at 10 mm high
from the skirt’s bottom.

Service limit:

39.9 mm

Measure the piston pin bore, and the piston pin
outer diameter.

Pin outer diameter service limit:

9.96 mm

Pin

bore service limit:

10.04 mm

Measure the connecting rod small end inner diameter
with a small bore diameter gauge.

Service limit:

14.06 mm

6.4 INSTALLATION

Install the piston rings with the marks facing up.
Do not damage the piston rings by spreading
the ends too far.

Clean the cylinder gasket surface being careful
not to drop any gasket material into the crankcase.

Apply some oil to inside of the connecting rod small end.
Install the piston, piston pin and clip.
Install the piston with the arrow mark facing
the exhaust pipe.
Do not align the piston pin clip end gap with
the piston cutout.

Install a new cylinder gasket.
Apply a thin coat of engine oil to the piston rings
and cylinder wall.
Install the cylinder, compressing the piston rings.
Replace a new cylinder head gasket.
Install the cylinder head.
Tighten the cylinder-mounting bolt.

The torque is 10-14N.m

7.2 THE PARTS DRAWING OF TRANSMISSION

7. TRANSMISSION SYSTEM

7.1 TROUBLE SHOOTING

7.6 GEAR BOX

SYSTEM

7.7 ELECTRIC SELF-STARTER MECHANISM

7.3 SHIFT MECHANISM (INCLUDE C.D.I)

7.4 AUTOMATIC CONTINUOUS VARIABLE
TRANSMISSION

7.5 CONTINUOUS VARIABLE TRANSMISSION

7.8 KICK STARTER

7.9 DISASSEMBLY AND CHECK OF C.V.T.
SYSTEM

7.1 TROUBLESHOOTING

ABNORMALLY ACT IN SHIFTING AND CAN’T RESET ★ FAULTY C.D.I

★ FAULTY SHIFT MOTOR

★ FAULTY SENSOR (F, N1, R, N2)

★ FAULTY SHIFT SPRING OR GEAR

CAN NOT MOVE AFTER ENGINE START

★ BELT WORN

★ FRONT PULLEY WORN OR BROKEN

★ LINING OF CLUTCH WORN

★ FAULTY SHIFT SPRING

CAN NOT RUN AT HIGH SPEED

★ BELT WORN

★ ROLLERS WORN

★ SPRING OF REAR PULLEY IS DISTORTED

ENGINE STOP AFTER SHIFT SUCCESSFULLY

★ FAULTY C.D.I

THE FUNCTION OF SPEED LIMITED IS ABNORMAL

★ FAULTY C.D.I

7.2 THE PARTS DRAWING OF TRANSMISSION SYSTEM

C.V.T

Shift Mechanism

Gear Box For

7.3 SHIFT MECHANISM

Sensor

Inspect wire for break or damage and check contact.
Measure sensor dimension as fig-1 after unscrew sensor.

fig-1

If length is below 30mm, it must be replaced.
Smear with loctite 5699 and screw with torque
25 kgf-cm in assembly.

SERVICE LIMITS: 30 mm
TORQUE: 25 kgf-cm

Shift Spring and Gear

Remove mission side cover and other parts.
Check shift gear for wear or damage.
Measure open width of shift spring as fig-2.

fig-2

If open width greater than 5mm, it must be replaced.

SERVICE LIMITS: 5 mm

Senso

r N2

Sensor R

Sensor

N1

Sensor

F

Shift

Motor

Shift Spring

Shift

Gear

data:

Shift Motor

Check shift motor whether it’s action is normal as follow

Disassembly mission side cover, parts of shift mechanism
and mission cover.
Get seal and bearing after disassembly shift motor of
mission cover.
Check seal and for wear or fatigue.
Replace it if necessary.

Seal

Bearing

Brush

7.4 AUTOMATIC CONTINUOUS VARIABLE TRANSMISSION

This transmission is the combination of automatic
centrifugal clutch and V-belt continuous variable
transmission, which can change the transmission
ratio automatically.

When engine speed increase, the drive pulley will
be push to belt by the centrifugal force from six rollers.
Then the pitch circle of belt in drive pulley will
be larger.
The belt at driven pulley is forced to move to
the center of shaft, then the radius of pitch circle
is decreased.
The transmission ratio is therefore altered by the
alteration of pitch circle’s radius.
(In the drawing, “H” means high speed, “L” means low speed)

7.5 CONTINUOUS VARIABLE TRANSMISSION

V-Belt

Made of rubber fiber, resistant to head, pressure and
abrasion. The inner side of the Belt is toothed.

Drive Pulley

Due to the increasing engine speed, the rollers push
the movable drive face by centrifugal force. Then the
belt is pressed and enlarges its turning radius.
The aluminum fan is installed on the exterior of fixed
drive face. It can reduce the belt temperature.

15 x11

Driven Pulley

Because the revolving radius of V-Belt at the Drive End is
enlarged, the Face Comp Movable Drive is squeezed out by
the V-Belt at the Driven End to shorten the revolving radius.
There is a Torque Cam on the Movable Drive Face.
Torque Cam is loaded from outside. When the outside load is
higher than the engine’s output, the pulley of fixed shaft and
belt slip to make the Movable Drive Face move along the inner
side of Cam and compensate to increase to high torque
(toward to low speed) and make the engine maintain
smooth running with original revolution.

7.6 GEAR BOX

Reverse Shaft Comp

Sensor

Drive Shaft
Comp

Drum Gear Shift

Fork

Fork Shaft

Coun

ter Shaft Comp

Remove mission side cover, parts of shift mechanism and mission cover.
Inspect gears for wear, scoring, chipping or break.
Replace it if necessary.

The gear ratio of front gear composition is about

47 31

The gear ratio of reverse gear composition is about

49

×49

×

31

7.7 ELECTRIC SELF-STARTER MECHANISM

15 16 11

Starter Motor is installed on the upper side of engine.
The starter motor can act only when the left hand brake
is applied.

ELECTRIC SELF-STARTER MECHANISM KICK STARTER

7.8 KICK STARTER

This kick-starter arm is on the left side of engine. When the kick-starter arm is kicked, the gear of start
shaft will drive the kick-starter to revolve the crankshaft to start the engine.
After the engine is started, the kick-started will stop transfer the power to the kick-starter driven gear.
When the kick-starter lever is released, the kick-starter gear will go back to its original position.

7.9 DISASSEMBLY AND CHECK OF C.V.T. SYSTEM

Remove the engine clutch cover, by unscrew
the fixed bolts.
Check the belt for wear. If necessary, replace the belt.
Disassembly the front drive pulley, check the six rollers
for wear. If necessary, replace the rollers.

8. STEERING SYSTEM

8.1 THE PARTS DRAWING OF STEERING SYSTEM 8.3 HANDLEBAR

8.2 TROUBLESHOOTING

8.4 STEERING SYSTEM

8.1 THE PARTS DRAWING OF STEERING SYSTEM

8.2 TROUBLESHOOTING

HARD STEERING

FRONT WHEEL WOBBLING

STEERS TO ONE SIDE

★ Faulty tire
★ Steering shaft holder too tight
★ Insufficient tire pressure
★ Faulty steering shaft bushing
★ Damaged steering shaft bushing

★ Faulty tire
★ Worn front brake drum bearing

★ Bent rim
★ Axle nut not tightened properly

★ Bent tie rods
★ Wheel installed incorrectly

★ Unequal tire pressure
★ Bent frame
★ Worn swing arm pivot bushings
★ Incorrect wheel alignment

FRONT SUSPENSION NOISE

★ Loose front suspension fasteners

★ Binding suspension link

HARD SUSPENSION

★ Faulty front swing arm bushings
★ Improperly installed front swing arms

★ Bent front shock absorber swing rod

SOFT SUSPENSION

★ Weak front shock absorber springs

★ Worn or damage front swing arm bushings

8.3 HANDLEBAR
REMOVAL

Remove the right side handlebar cover by unscrew two
fix screws.

Remove the throttle lever housing on the right
side handle bar.
Remove brake lever bracket as semb

Remove the handle bar switch on the left handle bar.
Remove rear brake lever bracket assembly.

Remove the bolts attaching the handlebar upper holder.
Remove the handlebar.

I INSTALLATION

Put the handlebar on the lower holders.
Make sure the handlebar punch mark match
with the top end of the handlebar lower holders. Install the
handlebar upper holders with
the L or R marks facing forward.
Tighten the forward bolts first, and then tighten the rear
bolts.
Install the handlebar upper holder’s cover.

Install the switch housing, aligning the boss with the hole.
Tighten the upper screw first then tighten the lower one.

Install the rear brake lever bracket, aligning the boss
with the hole.
Tighten the scre w securely.

Aligning the split line of the throttle housing

and holder with the punch mark. Tighten the screw
securely

8.4 THROTTLE HOUSING DISASSEMBLY

Unscrew the screws on the throttle housing cover.
Remove throttle housing cover and gasket. Disconnect
throttle cable from the throttle arm
and remove from the throttle housing.

Assembly is in the reverse order of
disassembly.

8.5 STEERING SYSTEM

Removal of Kingpin and Tie-rod

Remove the front wheels and brakes plates.
Remove the four self-lock nuts from the tie-rod ball joints
and take off the two tie-rods.

Remove the cotter pin on the kingpin.
Unscrew the bolt and remove the kingpin.

Tie-rod Inspection

Inspect the tie-rod for damage or bending. Inspect the
ball joint rubbers for damage, wear or deterioration.
Turn the ball joints with fingers. The ball joints should
turn smoothly and quietly.

Kingpin Inspection

Inspect the kingpin for damage or cracks.

Steering Shaft Removal

Remove the handle bar cover and handle bar.
(See paragraph 8-3)
Remove the front fender. (See paragraph 10-1) Remove
handlebar lower holder.
Unscrew steering shaft holder bolt, remove steering shaft
holder.
Take off the cotter pin below steering shaft. Unscrew the
steering shaft fixed out below shaft. Pull steering shaft
carefully.

Steering Shaft Holder Inspection

Remove the steering shaft.
Remove the bushing from the shaft.
Inspect the bushing for damage or wear, replace if
necessary. Measure the bushing inner diameter.

Maximum limit: Ø39.5 mm

Steering Shaft Inspection

Inspect the steering shaft for damage or cracks.

Installation of Steering Shaft

Apply grease to the holder.
Install the holder and oil seal tighten with the nuts.

Torq ue: 33 N.m (24 lbf-ft)

Install the steering shaft nut and tighten it.
This nut is under this steering shaft.

Torq ue: 50 N.m (37 lbf.ft)

Installation of Tie-rod

Install the ball joint with “ L” mark on the steering
shaft side.
Install the tie-rod with the mark on the wheel side.
Installation is in the reverse order of removal.

9. FRONT WHEEL SYSTEM

9.1 PART S DRAWING 9.2 TROUBLESHOOTING

9.3 FRONT WHEEL 9.4 FRONT BRAKES

9.1 PARTS DRAWING

FRONT WHEEL FRONT BRAKE

9.2 TROUBLESHOOTING

HARD STEERING ★ Faulty tire

★ Insufficient tire pressure

FRONT WHEEL WOBBLING ★ Faulty tire

★ Worn front brake drum bearing

★ Bent rim

★ Axle nut not tightened properly

BRAKE DRAG

★ Incorrect brake adjustment

★ Sticking brake cable

STEERS TO ONE SIDE

★ Bent tie rods
★ Wheel installed incorrectly
★ Unequal tire pressure
★ Incorrect wheel alignment

POOR BRAKE PERFORMANCE

★ Brake shoes worn

★ Worn brake drum
★ Brake linings oily, greasy or dirty
★ Improper brake adjustment

9.3 FRONT WHEELS

REMOVAL

Raise the front wheels off the ground by placing a jack
or other support under the frame.
Remove the front wheel nuts, washer and wheels.

INSTALLATION

Install and tighten the four-wheel castle nuts

Torq ue: 40-60 N.m (30-45 lbf.ft)

Remember put a cotter pin in the castle nut.

9.4 FRONT BRAKES

FRONT BRAKE INSPECTION

Remove the front wheel. Remove the brake drum.

Measure the brake lining thickness.

The minimum limit: 1.5 mm

If they are thinner than the minimum limit, replace the brake
linings.

Measure the brake drum inner diameter.

The maximum limit: 86 mm

Turn the inner race of each bearing with fingers.
The bearings should turn smoothly and quietly.
If the race does not turn smoothly or quietly,
remove and discard the bearings.

BRAKE PANEL REMOVAL

Disconnect the brake cable from the brake arm.
Remove the brake panel from the knuckle.

Remove brake arm and cam.
Remove return spring.
Remove indicator plate and felt seal.

INSTALL BRAKE PANEL

Apply grease to the brake cam and anchor pin
and install the cam in the brake panel.
Soak the felt seal in the engine oil and install the seal on the
brake cam.

Install the brake arm on the cam by aligning
the punch mark and the groove on the cam.
Tighten the brake arm bolt and nut.

Torq ue: 4-7 N.m

Install the return spring.

Install the brake panel on the knuckle.
Connect the brake cable to the brake arm.

Install the brake arm cover.
Tighten the screws securely.
Position the brake shoes in their original locations
and install the brake shoe spring.
Install the brake drum and front wheel.
Install the castle nut and cotter pin.

10. REAR WHEEL AND BRAKE SYSTEM

10.1 PART S DRAWING

10.3

DRIVE MECHANISM

10.2 TROUBLESHOOTING

10.4

HYFRAULIC DISC BRAKE SYSTEM

10.1 THE PARTS DRAWING OF REAR WHEEL SYSTEM

FOR ATV RXL70 AND RXL50M

FOR RXL 50/70/90/90R

★

BAD BRAKE

A

DJUSTMENT

★

BRAKE LININGS ARE OILY, GREASY OR DIRTY

★ BRAKE DRUMS ARE WORN
★ BRAKE ARM SETTING IS IMPROPERLY ENGAGE

V

IBRATION OR WOBBLE

★

AXLE IS NOT TIGHTENED WELL

★

BENT RIM

★

AXLE BEARINGS ARE WORN

★ FAULTY TIRES
★

REAR AXLE BEARING HOLDER IS FAULTY

10.2 TROUBLESHOOTING

BAD BRAKE PERFORMANCE

★ BRAKE SHOES ARE WORN

BRAKE DRAG

★ INCORRECT BRAKE ADJUSTMENT

★ STICKING BRAKE CAM
★ STICKING BRAKE CABLE

10.3 DRIVE MECHANISM

REMOVAL AND INSPECTION

Remove the rear wheel
Let the rear wheels off the ground.
Release the cotter pin, axle nut and washer.
Release the wheel and wheel hub.
Remove the drive chain under cover.

Disassemblies the chain retaining clip and master link.

Disassembly the driven sprocket, axle and sprocket
collar.
Check the driven sprocket for damage or wear.

Let the rear axle lie in V-blocks and check the run out.

The run out limit is 0.5 mm

Check the turning of bearing with fingers.
The bearings should turn smoothly and quietly.
Replace if necessary.

INSTALLATION

Add grease to the dust seal lips and install dust seals.
Assembly the rear axle and the driven sprocket.

Assembly the drive chain on the driven sprocket.
Assembly the master link and retaining clip.
Note the retaining clip direction.
Install the drive chain cover.
Assembly the chain under cover.

Assembly the wheel.

Tighten the rear axle nut with 60-80 N.m.

Install a new cotter pin.
Adjust rear brake level free play.
Adjust chain slack.

10.4 HYFRAULIC DISC BRAKE SYSTEM

To replace brake disc
To replace brake disc
Remove the rear left tire

Unscrew the two bolts shown on the photo and
remove caliper

Unscrew the rear wheel axle nut and then remove
the mounting seat of the disc

Unscrew bolts and remove the brake disc
Check the thickness of disc and replace a new one

if the thickness less than 3mm

TO REPLACE THE BRAKE SHOE

Remove the rear left tire

Unscrew the two bolts shown on the photo and
remove caliper

Press the plate to the end

Remove the brake shoe as shown

Check the thickness of brake shoe and replace
a new one if the thickness less than 1mm.

Press the piston to the end prior to installation of
brake shoe

Piston

TO REPLACE THE BRAKE HYDRAULIC OIL

Unscrew the bolts and open the cover.

Unscrew the bolt and drain out the used oil drain.
Fasten the bolt after the used oil being drained out
completely.

Add the brake oil (Dot 3 or Dot 4)
Keep oil level at least half of the cup to avoid
air gets into brake system, such like caliper and tube

Unscrew the bolt to vent air from brake system.
Fasten the bolt if there isn’t any air in
the brake system.

Pull left brake lever slightly to extract air from
brake system

Fill the brake oil to the level shown on the cup
when no air comes out
Assemble the cover

11. FENDERS AND EXHAUST PIPE

11.1 FENDERS DR

A

W

ING

For

Yukon

ST

EXL-50

For

V

ipe

r

ST

EXL-50

EXHAUST PIPE (For

all serials)

11.1 FENDRES DRAWING

11.4 CENTRAL-REAR-TRIM REMOVAL

11.2 REAR FENDERS REMOVAL

11.5 FRONT FENDER REMOVAL

11.3 FRONT-TRIM REMOVAL

11.6 EXHAUST PIPE REMOVAL

For E-MARK

11.2 REAR FENDERS REMOVAL

Pull the “Seat Release Bar” to take off the seat.
This seat release bar is under the right side of the
rear fender.

Procedures of remove the rear fender:
Remove the rear rack.
Unscrew the two bolts which connect the front fender and
rear fender.
Unscrew the two bolts, which connect the rear tender
and frame, these two bolts just below the seat.

Unscrew the six screws, which connect with footrest plate.
Pull the rear fender backward.
So the rear fender can be removed.

(Viper. St)
Pull the seat handle first.

There are two screws on the top of seat compartment.
Please remove them.

Then there are two screws on side of the tail.

Finally, you must remove the screws on the footrest.

11.3 FRONT-TRIM REMOVAL

Unscrew the two screws just below the headlight
of central-front-trim.
Unscrew the two screw which between central­front-trim and central-rear-trim.
Then remove the and headlight together.

(YukonST)

(Viper. St)

11.4 CENTRAL-REAR-TRIM REMOVAL

Remove the fuel tank cap.
Remove the central-rear-trim two mounting bolts from
the fuel tank.
Pull the central-rear-trim up ward.

11.5 FRONT FENDER REMOVAL

After remove the rear fender, central-front-trim and
central-rear-trim, remove the two front fender mounting
bolts from front frame.

Remove the mounting bolts and nuts from the front fender
and footrest plate.

(Viper. St)

Please remove the two screws on the top of the headlight.

Then you can see there is a screw on the tip of the vehicle.
Please remove it.

And there are the screws on the both side of the vehicle.
You can see it inside of the front fender.
After you remove those screws above, you still must follow
the procedure of 11.2 and 11.3. That’s the entire front fender
could be removed.

11.6EXHAUST PIPE REMOVAL

You must wait at least 15 minutes after turn off the engine.
You

need remove the seat, rear fender and footrest plate,

before

you take off the exhaust pipe.

Unscrew the two exhaust pipe bolts that fixed with engine.
NOTE

：Do

not service the exhaust pipe while they are hot.

Remove the exhaust pipe bolt mounting on the frame
below the

seat,

and the other one Is on the side of the

transmission

.

Remove the exhaust pipe carefully.

EXHAUST PIPE INSTALLATION

Installation is the reverse order of removal.

Torque:

Exhaust muffler bolts 30 N.m (22 lbf.ft)

After installation, make sure that there are no exhaust leaks.

11.6EXHAUST PIPE REMOVAL For E-MARK

You must wait at least 15 minutes after turn off the engine.
You

need remove the seat, rear fender and footrest plate,

before

you take off the exhaust pipe.

Unscrew the two exhaust pipe bolts that fixed with engine.
NOTE

：Do

not service the exhaust pipe while they are hot.

Remove

the four bolts on the

front drive chain cover,

remove the

cover,and take apart the connecting tube.

Remove the exhaust pipe bolt mounting on the frame
below the

seat.

Remove the exhaust pipe carefully.

For E-MARK

12. ELECTRICAL SYSTEM

12.1 TROUBLESHOOTING

12.5 CHARGING

12.2 IGNITION COIL

12.6 ELECTRIC STARTER

12.3 BATTERY CAUTION

12.4 BATTERY INSPECTION

12.7 WIRING DIAGRAMS

12.8

SPEEDOMETER AND FUEL METER

12.9

WIRING DIAGRAM

12.1 TROUBLESHOOTING

ENGINE STARTS BUT STOPS ★ IMPROPER IGNITION TIMING

★ FAULTY SPARK PLUG

NO SPARK AT PLUG ★ ENGINE STOP SWITCH AT “ OFF “

★ FAULTY IGNITION COIL
★ FAULTY GENERATOR
★ FAULTY CDI UNIT
★ POOLY CONNECTED:

Between CDI and ignition coil
Between alternator and CDI unit
Between CDI and engine stop switch
Between ignition coil and spark plug
Between generator and CDI unit

ENGINE STARTS BUT RUNS POORLY ★ IGNITION PRIMARY CIRCUIT

Faulty generator
Faulty CDI unit
Faulty alternator exciter coil
Loosen contacted terminals
Faulty ignition coil

★ IGNITION SECONDARY CIRCUIT

Faulty plug
Loosen contacted spark plug wire

★ IMPROPER IGNITION TIMING

Faulty generator
Faulty CDI unit

CHARGING SYSTEM FAILURE ★ LOOSE, BROKEN OR SHORTED WIRE

★ FAULTY ALTERNATOR
★ FAULTY IGNITION SWITCH

ENGINE INTERMITTENT POWER ★ LOOSE BATTERY CONNECTION

★ LOOSE CHARGING SYSTEM CONNECTION

STARTER MOTOR WILL NOT TURN ★ DEAD BATTERY

★ FAULTY IGNITION SWITCH
★ LOOSE OR DISCONNECTED WIRE

STARTER MOTOR AND ENGINE TURN, ★ FAULTY IGNITION SYSTEM
BUT ENGINE DOES NOT START

★ ENGINE PROBLEMS

★ FAULTY ENGINE STOP SWITCH

REMOTE CONTROLLER INCAPABLE ACTION

★ FAULTY REMOTE CONTROLLER

TO MAKE ENGINE UNABLE RUNNING

★ SCANTY CONTROLLER BATTERY

ELECTRIC

12.2 IGNITION COIL

Remove the spark plug cap from the spark plug

Disconnect the ignition coil primary wire.

Measure the primary coil resistance.

STANDARD: 0.1 - 0.3Ω(20℃)

Measure the secondary coil resistance with
the spark plug cap in place.

STANDARD : 7.4 – 12 kΩ(20℃)

IGNITION TIMING

The ignition advance is 15°± 3°

/4000rpm

The Capacitive Discharge Ignition (CDI) system is factory pre-set and does not require adjustment.

ALTERNATOR EXCITER COIL

Remove the seat / rear fender and front fender. (see chapter 10)
Disconnect the exciter coil wire.
Measure the resistance between the yellow / red wire and ground.

STANDER : 460-700Ω

(AT 20℃, 68℉)

12.3 BATTERY CAUTION

The battery gives off explosive gases; keep sparks, flames and cigarettes away. Provide adequate
ventilation when charging or using the battery in an open area. The battery contains sulfuric acid
(electrolyte). Contact with skin or eyes may cause severe burns. Wear protective clothing and a face shield.
Electrolyte is poisonous. If swallowed drink large quantities of water or milk and call a physician.

12.4 BATTERY INSPECTION

Battery is under the seat, you can see this battery from the
left side.
Measure the battery voltage using a voltmeter.

VOLTAGE: Fully charged: 13.1 V Undercharged: Below

12.0 V

BATTERY REMOVAL

Remove the battery holder bolt nuts.
Disconnect the negative cable and then
the position cable and remove the battery.

BATTERY INSTALLATION

Install the battery in the reverse order of removal. After
installing the battery, coat the terminals with clean grease.

12.5 CHARGING

Connect the charge positive cable to the battery position
terminal.
Connect the charge negative cable to the battery negative
terminal.
Using 0.9A-charging current about 5 hours. (Normal
charging) Or using 4A-charging current about 1 hour.
(Quick charging) Keep flames and sparks away from a
battery being charged. Quick charging should be limited to
an emergency;
Normal charging is preferred.

12.6 ELECTRIC STARTER Information

A week battery may be unable to run the starter motor
quickly enough. If the battery voltage is enough while the
engine is not Cranking, the starter motor
may be damaged.

TROUBLESHOOTING

Starter Motor Turns Slowly

Weak battery.
Poorly connected starter motor cable.
Failed starter motor.
Poorly connected battery ground cable.

Starter Motor Not Turn

Engine stop switch at “off “position.
Gearshift bar is not at neutral position.
Check for a blown fuse near battery.
Make sure that the battery is fully charged and in good condition.

12.7 LIGHT BULBS REPLACEMENT

HEADLIGHT

For (Viper.St EXL-50)
After you remove the screws on the top of headlight,
it can be take off. Be careful around the headlight, there
are many pins mold on the plastic.

Remove the handle bar cover. Remove the central–front
cover with headlight together.

(The right side picture is for YukonST EXL-50)

Remove the bulb socket by turning it counterclockwise
Replace the bulb with a new one
Install the removed parts in the reverse order of removed

TAILLIGHT

Install the remove parts in the reverse order of remova

For (Viper.St EXL-50) For( Yukon

ST

EXL-50)

12.8 SPEED METER AND FUEL METER

PARTS DRAWING

Picture of right side is for YukonST EXL-50

For Viper.ST EXL-50

REMOVAL

THE HEADLIGHT PHOTOGRAPH--EXL 150 (2004 two-passengers)

EXL 150(Viper. St) have another shape but its cables position
are the same as EXL 150(2004 two-passenger)

ELECTRICAL
SPEEDMETER

FUEL

METER CABLE

METER
SENSOR

METER CABLE

METER CABLE

12.9 WIRING DIAGRAM

This diagram is for Viper. St EXL-50

This diagram is for YukonST EXL-50

N.G

.

CHECK FUEL FLOW TO CARBURETOR

O.K.

N.G

.

SPARK TEST

WEEK OR NO SPARK

O.K.

TEST CYLINDER COMPRESSION

LOW COMPRESSION

O.K.

START THE ENGING

ENGINE DOES NOT FIRE

13.TROUBLESHOOTING

13.1 ENGINE DOES NOT START

13.4 LOSS POWER

13.2 POOR PERFORMANCE AT LOW AND IDLE SPEEDS 13.5 POOR HANDLING

13.3 POOR PERFORMANCE AT HIGH SPEED

13.1 ENGINE DOES NOT START

N.G.

POSSSIBLE REASON

★ No fuel In fuel tank
★ Clogged float valve

★ Clogged fuel tank cap breather hole
★ Clogged at fuel tube

★ Faulty spark plug
★ Fouled spark plug
★ Faulty CDI unit
★ Faulty alternator
★ Faulty engine stop switch
★ Poorly connected ,broken or shorted wires
★ Broken or shorted ignition coil
★ Broken or shorted spark plug wire
★ Faulty pulse generator
★ Faulty ignition switch

★ Worn cylinder and piston rings
★ Damaged cylinder head gasket

ENGINE START BUT STOPS

★ Auto choke off or damaged
★ Auto choke power wire disconnected
★ Improperly adjusted air screw
★ Improperly ignition timing
★ Fuel / air mixture ratio is too lean

REMOVE AND INSPECT SPARK PLUG

WET PLUG

★ Carburetor flooded
★ Improperly adjusted air screw

★ Fuel / air mixture ratio too rich
★ Auto choke stuck or damaged
★ Air cleaner dirty

N.G.

CHECK carburetor
AIR SCREW ADJUSTMENT

N.G

CHECK FOR LEAKING
INTAKE PIPE

O.K.

CHECK IGNITION TIMI

T FUEL FLOW RESTRICTED

CHECK FUEL TUBE A
CARBURETOR

FUEL FLOWS FREELY

CLOGGED

REMOVE CARBURETOR
CHECK FOR CLOGGED JET

NOT CLOGGED

13.2 POOR PERFORMANCE AT LOW AND IDLE SPEEDS

CHECK IGNITION TIMING

O.K.

N.G.

POSSIBLE REASON

★ Faulty CDI unit or pulse generator

★ Improperly adjusted air screw

★ Deteriorated insulator o-ring
★ Loose carburetor

PERFORM SPARK TEST

WEEK OR INTERMITTENT SPARK

★ Loose or disconnected ignition system wires
★ Faulty ,carbon or wet fouled spark plug
★ Faulty alternator
★ Faulty CDI unit
★ Faulty ignition switch
★ Faulty ignition coil
★ Faulty pulse generator

★ Broken or shorted spark plug wire
★ Faulty engine stop switch

13.3 POOR PERFORMANCE AT HIGH SPEED

N.G.

N

CHECK AIR CLEANER DIRTY
FILTER ELEMENT

POSSIBLE REASON

★

Faulty CDI unit

★ Faulty pulse generator

★ Lack of fuel in tank
★ Clogged fuel line

★ Clogged fuel valve
★ Logged fuel tank breather hole

★ Clean with high pressure air gun

★ Clean the filter

PESSURE LOW CHECKTIRE

CHECK TIRE PRESSURE

PRESSURE NORMAL

ACCELERATE LIGHTY

ENGINE SPEED DOES
NOT INCREASE

ENGINE SPEED INCREASE

N.G

.

CHECK IGNITION TIMING

CHECK CARBURETOR

O.K.

FOULED OR DISCOLOED

CHECK SPARK PLUG

O.K.

OVERHEATING

CHECK FOR ENGINE
OVERHEATING

O.K.

13.4 LOSS POWER

RAISE WHEELS OFF GROUND DOES NOT SPIN FREELY
AND SPIN BY HAND

SPIN FREELY

POSSIBLE REASON

★ Brake dragging
★ Drive chain too tight

★ Damaged wheel bearing
★ Wheel bearing needs lubrication

★ Punctured tire
★ Faulty tire valve

★ Fuel / air mixture ratio too rich or lean
★ Clogged in air cleaner

★ Clogged in muffler
★ Restricted fuel flow
★ Clogged fuel tank cap breather hole

TEST CYLINDER COMPRESSION

O.K.

ACCELERATE OR RUN
AT HIGH SPEED

TOO LOW

CLOGGED

KNOCKS

★ Faulty pulse generator
★ Faulty CDI unit

★ Leaking head gasket
★ Worn cylinder and piston rings

★ Clean

★ Clean the spark plug
★ Spark plug is incorrect heat range

★ Excessive carbon deposited in

Combustion chamber

★ Wrong type of fuel
★ Fuel / air mixture ratio is lean
★ Use of poor quality fuel

★ worn piston and cylinder
★ Fuel / air mixture ratio is lean

★ Wrong type of fuel
★ Ignition timing too advanced
★ Excessive carbon deposited in

Combustion chamber

13.5 POOR HANDLING

POSSIBLE REASON

STEERING IS HEAVY

ONE WHEEL IS WOBBLING

VEHICLE PULLS TO ONE SIDE

★ Damaged steering bearing
★ Damaged steering shaft bushing

★ Bent rim
★ Improperly installed wheel hub

★ Excessive wheel bearing play
★ Bent swingarm
★ Bent frame
★ Swing arm pivot bushing excessively
★ Worn

★ Bent tie-rod
★ Incorrect tie-rod adjustment

★ Rear tie air pressure incorrect
★ Improper wheel alignment

★ Bent frame