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8
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CHAPTER 8°
TROUBLESHOOTING
FAILURE TO START/DIFFICULTIES IN STARTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1
FUEL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1
ELECTRICAL SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2
POOR ENGINE COMPRESSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2
POOR PERFORMANCE AT IDLE SPEED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3
UNSATISFACTORY PERFORMANCE AT MEDIUM-HIGH SPEED . . . . . . . . . . . . . . . . . 8-3
DIFFICULTIES IN SHIFTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
SHIFTING IMPOSSIBLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
THE SHIFT PEDAL FAILS TO MOVE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
DISENGAGING GEARS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-4
CLUTCH SLIDES OR FAILS TO RELEASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5
CLUTCH SLIDES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5
CLUTCH FAILS TO RELEASE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-5
DEFECTIVE BRAKES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6
POOR BRAKING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6
OIL LEAKS OR MALFUNCTIONING OF FRONT FORK . . . . . . . . . . . . . . . . . . . . . . . . . 8-6
OIL LEAKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6
MALFUNCTIONING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-6
UNSTABLE STEERING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7
DEFECTIVE FUNCTIONING OF LIGHTS AND INDICATORS . . . . . . . . . . . . . . . . . . . . . 8-8
POOR HEADLIGHT ILLUMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8
FREQUENT BURNING OF BULB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8
DIRECTION INDICATORS FAIL TO TURN ON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8
DIRECTION INDICATORS FAIL TO TURN OFF . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-8
DELAYED TURNING ON OF INDICATORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9
EXCESSIVE INDICATOR INTERMITTENCE FREQUENCY . . . . . . . . . . . . . . . . . . . 8-9
THE HORN FAILS TO WORK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9
OVERHEATING OF ENGINE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-9
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Page 372 of 382
FAILURE TO START/
DIFFICULTIES IN STARTING
8-1
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TROUBLESHOOTING
NOTE:
The troubleshooting tables that follow do not identify every cause of trouble. They may however prove
helpful as a guide to identifying trouble. To inspect, adjust or replace parts, refer to the appropriate sec-
tion in the manual.
FAILURE TO START/DIFFICULTIES IN STARTING
FUEL SYSTEM
Fuel tank
Fuel cock
Carburetor
Air filter PROBABLE CAUSES
•Empty
•Fuel filter obstructed
•Fuel tank air cap passage obstructed
•Petrol contains water or impurities or is adulterated
•Hose obstructed
•Fuel filter obstructed
•Petrol contains water or impurities or is adulterated
•Pilot jet obstructed
•Pilot air passage obstructed
•Infiltrations of air
•Deformation of float
•Needle valve worn or scratched
•Needle valve seat insufficiently sealed
•Fuel level set wrongly
•Pilot jet set wrongly
•Starter jet obstructed
•Malfunctioning of the starter piston
•Air filter element obstructed
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FAILURE TO START/
DIFFICULTIES IN STARTING
8-2
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Spark plug
Ignition coil
Ignition unit
Switches and cables PROBABLE CAUSES•Electrodes gap not correct
•Electrodes worn
•Feed cable interrupted
•Wrong thermal grading of spark plug
•Defective spark plug cap
•Primary or secondary winding interrupted
•High voltage cable defective
•Defective coil
•Defective unit
•Defective pick-up coil
•Woodruff key broken
Starter motor
•Starter motor defective
•Starter motor relay defective
•Diodes defectives
•Starter one-way bearing defective
•Main switch defective
•Emergency stop engine switch defective
•Harness with cable interrupted
•Neutral switch defective
•Sidestand switch defective
•Clutch switch defective
•Starter switch defective
ELECTRICAL SYSTEM
Cylinder and cylinder head
Piston and piston rings
Crankcase and valves, crankshaft PROBABLE CAUSES
•Spark plug tightening insufficiently
•Cylinder head or cylinder insufficiently tightened
•Cylinder head gasket broken
•Cylinder gasket broken
•Cylinder worn, damaged or seized
•Piston rings wrongly assembled
•Piston rings worn, yielded or broken
•Piston rings stuck together
•Piston seized or damaged
•Poor crankcase sealing
•Crankshaft oil seal edge damaged
•Poor valve sealing
•Valve and seat with insufficient contact
•Valve timing wrongly
•Valve spring broken
•Crankshaft seized
•Camshaft seized
POOR ENGINE COMPRESSION
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POOR PERFORMANCE AT IDLE SPEED/
UNSATISFACTORY PERFORMANCE AT MEDIUM-HIGH SPEED
8-3
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Carburetor
Electrical system
Valves PROBABLE CAUSES•The starter piston fails to return freely
•Pilot jet obstructed or loose
•Pilot jet obstructed
•Pilot air screw wrongly set
•Idle speed wrongly set
(throttle valve stop screw)
•Throttle cable free play wrongly set
•Carburetor flooded
•Valve clearance wrongly set
Air filter
•Air filter element obstructed
POOR PERFORMANCE AT IDLE SPEED
See “FAILURE TO START/DIFFICULTIES IN STARTING”.
(FUEL SYSTEM, ELECTRICAL SYSTEM, COMPRESSION SYSTEM and Valve clearance)
Carburetor
PROBABLE CAUSES
•Petrol contains water or impurities or is adulterated
•Infiltrations of air
•Deformation of float
•Defective diaphragm
• Needle valve worn or scratched
•Needle valve seat insufficiently sealed
•Needle stop position incorrect
•Fuel level set wrongly
•Main jet obstructed or loose
•Main nozzle obstructed or loose
UNSATISFACTORY PERFORMANCE AT MEDIUM-HIGH SPEED
•Defective battery
•Defective spark plug
•Defective ignition unit
•Defective AC magneto
•Defective ignition coil
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Page 375 of 382

DIFFICULTIES IN SHIFTING
8-4
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Clutch
Engine oil PROBABLE CAUSES•Clutch cable wrongly set
•Wrong position of push lever
•Irregular engagement of push lever and push
rod
•Pressure plate deformed
•Clutch springs not preloaded uniformly
•Reference marks not aligned
•Push rod broken
•Clutch gear assy nut loose or push rod deformed
•Primary driven gear bearing defective
•Driven plates deformed
•Driving plates deformed
•Clutch cable damaged
•Oil level over maximum
•Incorrect gradation (high viscosity)
•Degradation
SHIFTING IMPOSSIBLE
DIFFICULTIES IN SHIFTING
Shift shaft
Shift cam, shift fork PROBABLE CAUSES•Shift shaft deformed
•Groove with impurities or foreign bodies
•Shift fork stuck
•Shift fork guide bar deformed
THE SHIFT PEDAL FAILS TO MOVE
Transmission•Transmission gears struck
•Gears stuck by impurities or foreign bodies
•Wrong transmission assembly
Shift shaft
Shift fork PROBABLE CAUSES•Shift lever set wrongly
•Shift cam
stop lever fails to return freely
•Shift forks worn
Transmission
•Gear clutches worn
DISENGAGING GEARS
Shift cam
•Shaft cam with thrust free play
•Shift cam groove worn
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Page 376 of 382
CLUTCH SLIDES OR FAILS TO RELEASE
8-5
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Clutch
Engine oil PROBABLE CAUSES•Clutch cable wrongly set
•Clutch springs loose
•Clutch spring yielded
•Friction plates worn
•Clutch plates worn
•Clutch improperly assembled
•Oil level below minimum
•Incorrect gradation (low viscosity)
•Degradation
CLUTCH SLIDES
CLUTCH SLIDES OR FAILS TO RELEASE
Refer to “SHIFTING IMPOSSIBLE” section.
CLUTCH FAILS TO RELEASE
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