APPENDIX 17-17 Troubleshooting Guide

Cylinder, piston worn

Piston ring bad (worn, weak, broken, or

sticking) Piston ring/groove clearance excessive Cylinder head warped Cylinder head gasket damaged Valve spring broken or weak Valve not seating properly (valve bent,

worn, or carbon accumulation on the

seating surface)

Other:

IC igniter trouble

Carburetor vacuum piston doesn’t slide smoothly

Carburetor vacuum piston diaphragm dam­age

Engine oil viscosity too high

Drive train trouble

Brake dragging

Air suction valve trouble

Vacuum switch valve trouble

Coasting enricher trouble

Poor Running or No Power at High Speed: Firing incorrect:

Spark plug dirty, broken, or maladjusted

Spark plug cap or high tension wiring trou­ble

Spark plug cap shorted or not in good con­tact

Spark plug incorrect

IC igniter trouble

Crankshaft sensor trouble

Ignition coil trouble

Fuel/air mixture incorrect:

Starter plunger stuck open

Main jet clogged or wrong size

Jet needle or needle jet worn

Air jet clogged

Fuel level in carburetor float bowl too high or too low

Bleed holes of needle jet holder or needle jet clogged

Air cleaner clogged, poorly sealed, or miss­ing

Air cleaner duct loose

Air cleaner O-ring damaged

Water or foreign matter in fuel

Carburetor holder loose

Fuel tank air vent obstructed

Fuel tap clogged

Fuel line clogged

Compression low:

Spark plug loose

Cylinder head not sufficiently tightened down

No valve clearance

Cylinder, piston worn

Piston ring bad (worn, weak, broken, or

sticking) Piston ring/groove clearance excessive Cylinder head gasket damaged Cylinder head warped Valve spring broken or weak Valve not seating properly (valve bent,

worn, or carbon accumulation on the

seating surface.)

Knocking:

Carbon built up in combustion chamber Fuel poor quality or incorrect Spark plug incorrect IC igniter trouble

Miscellaneous:

Throttle valve won’t fully open

Carburetor vacuum piston doesn’t slide smoothly

Carburetor vacuum piston diaphragm dam­aged

Brake dragging

Clutch slipping

Overheating

Engine oil level too high

Engine oil viscosity too high

Drive train trouble

Air suction valve trouble

Vacuum switch valve trouble

Coasting enricher trouble

Balancer mechanism malfunctioning

Overheating: Firing incorrect:

Spark plug dirty, broken, or maladjusted Spark plug incorrect IC igniter trouble

Fuel/air mixture incorrect:

Main jet clogged or wrong size

Fuel level in carburetor float bowl too low

Carburetor holder loose

Air cleaner duct loose

Air cleaner poorly sealed, or missing

Air cleaner O-ring damaged

Air cleaner clogged

Compression high:

Carbon built up in combustion chamber

Engine load faulty:

Clutch slipping Engine oil level too high Engine oil viscosity too high Drive train trouble Brake dragging

Lubrication inadequate:

Engine oil level too low

Engine oil poor quality or incorrect

17-18 APPENDIX Troubleshooting Guide Coolant incorrect:Shift drum groove worn Coolant level too low Gear positioning lever spring weak or bro- Coolant deteriorated ken Cooling system component incorrect:Shift fork pin worn Radiator fin damaged Drive shaft, output shaft, and/or gear Radiator clogged splines worn Thermostat trouble Overshifts: Radiator cap trouble Gear positioning lever spring weak or bro- Radiator fan switch trouble ken Fan motor broken Shift mechanism arm spring broken Fan blade damaged

Water pump not turning Water pump impeller damaged

Over Cooling: Cooling system component incorrect:

Radiator fan switch trouble Thermostat trouble

Clutch Operation Faulty: Clutch slipping:

Friction plate worn or warped Steel plate worn or warped Clutch spring broken or weak Clutch hub or housing unevenly worn No clutch lever play Clutch inner cable trouble Clutch release mechanism trouble

Clutch not disengaging properly:

Clutch plate warped or too rough Clutch spring compression uneven Engine oil deteriorated Engine oil viscosity too high Engine oil level too high Clutch housing frozen on drive shaft Clutch hub nut loose Clutch hub spline damaged Clutch friction plate installed wrong Clutch lever play excessive Clutch release mechanism trouble

Gear Shifting Faulty: Doesn’t go into gear; shift pedal doesn’t return:

Clutch not disengaging Shift fork bent or seized Gear stuck on the shaft Gear positioning lever binding Shift return spring weak or broken Shift return spring pin loose Shift mechanism arm spring broken Shift mechanism arm broken

Jumps out of gear:

Shift fork ear worn, bent

Gear groove worn

Gear dogs and/or dog holes worn

Abnormal Engine Noise: Knocking:

IC igniter trouble

Carbon built up in combustion chamber

Fuel poor quality or incorrect

Spark plug incorrect

Overheating

Piston slap:

Cylinder/piston clearance excessive Cylinder, piston worn Connecting rod bent Piston pin, piston pin hole worn

Valve noise:

Valve clearance incorrect Valve spring broken or weak Camshaft bearing worn Rocker arm worn Rocker shaft worn

Other noise:

Connecting rod small end clearance exces­sive

Connecting rod big end clearance exces­sive

Piston ring worn, broken, or stuck

Piston seizure, damage

Cylinder head gasket leaking

Exhaust pipe leaking at cylinder head con­nection

Crankshaft runout excessive

Engine mounts loose

Crankshaft bearing worn

Primary chain worn

Camshaft chain tensioner trouble

Camshaft chain, sprocket, guide worn

Air suction valve damaged

Vacuum switch valve damaged

Alternator rotor loose

Balancer gear worn or chipped

Balancer shaft position maladjusted

Balancer bearing worn

Starter chain, sprocket, guide worn

Abnormal Drive Train Noise: Clutch noise:

Clutch housing/friction plate clearance ex­cessive