Honda Motorcycle Troubleshooting Guide
Classic Cycles Technical Resources
NOTE
*This is not an exhaustive list,giving every possible
cause for each problem listed. It is meant simply as a
rough guide to assist the troubleshooting for some of
the more common difficulties.
Engine Doesn't Start, Starting Difficulty:
Starter motor not rotating:
Starter lockout or neutral switch trouble
Starter motor trouble
Battery voltage low
Relays not contacting or operating
Starter button not contacting
Wiring open or shorted
Ignition switch trouble
Engine stop switch trouble
Fuse blown
Starter motor rotating but engine doesn't turn over:
Starter clutch trouble
Engine won't turn over:
Valve seizure
Cylinder, piston seizure
Crankshaft seizure
Connecting rod small end seizure
Connecting rod big end seizure
Transmission gear or bearing seizure
Camshaft seizure
Balancer bearing seizure
No fuel flow:
Fuel tap vacuum hose clogged
Fuel tank air vent obstructed
Fuel tap clogged
Fuel line clogged
Float valve clogged
Engine flooded:
Fuel level in carburetor float bowl too high
Float valve worn or stuck open
Starting technique faulty
(When flooded, crank the engine with the throttle
fully open to allow more air to reach the
engine.)
No spark; spark weak:
Battery voltage low
Spark plug dirty, broken, or maladjusted
Spark plug cap or high tension wiring trouble
Spark plug cap not in good contact
Spark plug incorrect
IC ignitor trouble
Neutral, starter lockout, or side stand switch
trouble
Pickup coil trouble
Ignition coil trouble
Ignition or engine stop switch shorted
Wiring shorted or open
Fuse blown
Compression low:
Spark plug loose
Cylinder head not sufficiently tightened down
Cylinder, piston worn
Piston ring bad (worn, weak broken, or sticking)
Piston ring/land 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)
Hydraulic lash adjuster damaged (worn, seizure, or
spring broken)
Hydraulic lash adjuster oil passage clogged
Poor Running at Low Speed:
Spark weak:
Battery voltage low
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 ignitor trouble
Pickup coil trouble
Ignition coil trouble
Fuel/air mixture incorrect:
Pilot screw maladjusted
Pilot jet, or air passage clogged
Air bleed pipe, bleed holes clogged
Pilot passage clogged
Air cleaner clogged, poorly sealed, or missing
Starter plunger stuck open
Fuel level in carburetor float chamber too high or
too low
Fuel tank air vent obstructed
Carburetor holder loose
Surge tank duct loose
Compression low:
Spark plug loose
Cylinder head not sufficiently tightened down
Cylinder, piston worn
Piston ring bad (worn, weak, broken, or sticking)
Piston ring/land clearance excessive
Cylinder head warped
Cylinder head gasket damaged
Engine not sufficiently warmed up after lash
adjuster installation
Hydraulic lash adjuster damaged (worn, seizure, or
spring broken)
Hydraulic lash adjuster oil passage clogged
Valve spring broken or weak
Valve not seating properly (valve bent, worn, or
carbon accumulation on the seating surface)
Backfiring when deceleration:
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Vacuum switch valve broken
Air suction valve trouble
Coasting enricher trouble
Other:
IC ignitor trouble
Carburetors not synchronizing
Carburetor vacuum piston doesn't slide smoothly
Engine oil viscosity too high
Drive train trouble
Final gear case oil viscosity too high
Brake dragging
Air suction valve trouble
Vacuum switch valve trouble
Poor Running or No Power at High Speed:
Firing incorrect:
Spark plug dirty, broken, or maladjusted
Spark plug cap shorted or not in good contact
Spark plug incorrect
IC ignitor trouble
Pickup coil 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 chamber too high or
too low
Bleed holes of air bleed pipe or needle jet clogged
Air cleaner clogged, poorly sealed, or missing
Surge tank duct poorly sealed
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
Cylinder, piston worn
Piston ring bad (worn, weak, broken, or sticking)
Piston ring/land clearance excessive
Cylinder head gasket damaged
Cylinder head warped
Hydraulic lash adjuster damaged (worn, seizure, or
spring broken)
Hydraulic lash adjuster oil passage clogged
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 ignitor trouble
Backfiring when deceleration:
Vacuum switch valve broken
Air suction valve trouble
Coasting enricher trouble
Miscellaneous:
Throttle valve won't fully open
Carburetor vacuum piston doesn't slide smoothly
Brake dragging
Clutch slipping
Overheating
Engine oil level too high
Engine oil viscosity too high
Drive train trouble
Final gear case oil viscosity too high
Air suction valve trouble
Vacuum switch valve trouble
Balancer mechanism malfunctioning
Overheating:
Firing incorrect:
Spark plug dirty, broken, or maladjusted
Spark plug incorrect
IC ignitor trouble
Fuel/air mixture incorrect:
Main jet clogged or wrong size
Fuel level in carburetor float chamber too low
Carburetor holder loose
Air cleaner poorly sealed, or missing
Air cleaner duct poorly sealed
Air cleaner ciogged
Surge tank duct poorly sealed
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
Final gear case oil viscosity too high
Brake dragging
Lubrication inadequate:
Engine oil level too low
Engine oil poor quality or incorrect
Gauge incorrect:
Water temperature gauge broken
Water temperature sensor broken
Coolant incorrect:
Coolant level too low
Coolant deteriorated
Cooling system component incorrect:
Radiator clogged
Thermostat trouble
Radiator cap trouble
Thermostatic fan switch trouble
Fan relay in junction box trouble
Fan motor broken
Fan blade damaged
Water pump not turning
Water pump impeller damaged
Over Cooling:
Gauge incorrect:
Water temperature gauge broken
Water temperature sensor broken
Cooling system component incorrect:
Classic Cycles Technical Resources
Thermostatic fan switch trouble
Thermostat trouble
Clutch Operation Faulty:
Clutch slipping:
No clutch lever play
Friction plate worn or warped
Steel plate worn or warped
Clutch spring broken or weak
Clutch release mechanism trouble
Clutch hub or housing unevenly worn
Clutch inner cable catching
Clutch not disengaging properly:
Clutch lever play excessive
Clutch plate warped or too rough
Clutch spring compression uneven
Engine oil deteriorated
Engine oil viscosity too high
Engineoil level too high
Clutch housing frozen on drive shaft
Clutch release mechanism trouble
Clutch hub locknut loose
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 position lever binding
Shift return spring weak or broken
Shift return spring pin loose
Shift mechanism arm spring broken
Shift mechanism arm broken
Shift pawl broken
Jumps out of gear:
Shift fork worn
Gear groove worn
Gear dogs and/or dog holes worn
Shift drum groove worn
Gear positioning lever spring weak or broken
Shiftfork pin worn
Drive shaft, output shaft, and/or gear splines worn
Overshifts:
Gear positioning lever spring weak or broken
Shift mechanism arm spring broken
Piston slap:
Cylinder/piston clearance excessive
Cylinder, piston worn
Connecting rod bent
Piston pin, piston holes worn
Valve noise:
Engine not sufficiently warmed up after lash
adjuster installation
Hydraulic lash adjuster damaged (worn, seizure, or
spring broken)
Air in hydraulic lash adjuster
Metal chips or dust jammed in hydraulic lash
adjuster
Engine operated in red zone
Valve spring broken or weak
Camshaft bearing 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 gear worn or chipped
Camshaft chain tensioner trouble
Upper or lower tension spring trouble
Camshaft chain, sprocket, guide worn
Air suction valve damaged
Balancer gear worn or chipped
Balancer shaft position maladjusted
Balancer bearing worn
Balancer coupling rubber damper damaged
Oil pump chain, sprocket worn
Abnormal Drive Train Noise:
Clutch noise:
Weak or damaged rubber damper
Clutch housing/friction plate clearance excessive
Clutch housing gear worn
Transmission noise:
Bearings worn
Transmission gears worn or chipped
Metal chips jammed in gear teeth
Engine oil insufficient
Drive line noise:
Bevel gear bearings worn
Bevel gears worn or chipped
Bevel gears maladjusted
Rear wheel coupling damaged
Insufficient lubricant
Abnormal Engine Noise:
Knocking:
IC ignitor trouble
Carbon built up in combustion chamber
Fuel poor quality or incorrect
Spark plug incorrect
Overheating
Abnormal Frame Noise:
Front fork noise:
Oil insufficient or too thin
Spring weak or broken
Rear shock absorber noise:
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Shock absorber damaged
Disc brake noise:
Pad installed incorrectly
Pad surface glazed
Discwarped
Caliper trouble
Drum brake noise:
Brake linings overworn or worn unevenly
Drum worn unevenly or scored
Brake springs weak or broken
Foreign matter in hub
Brake not properly adjusted
Other noise:
Bracket, nut, bolt, etc. not properly mounted or
tightened
Oil Pressure Warning Light Goes On:
Engine oil pump damaged
Engine oil screen clogged
Engine oil filter clogged
Engine oil level too low
Engine oil viscosity too low
Camshaft bearings worn
Crankshaft bearings worn
Oil pressure switch damaged
Wiring damaged
Relief valve stuck open
O-ring at the oil pipe in the crankcase damaged
Exhaust Smokes Excessively:
White smoke:
Piston oil ring worn
Cylinder worn
Valve oil seal damaged
Valve guide worn
Engineoil level too high
Black smoke:
Air cleaner clogged
Main jet too large or fallen off
Starter plunger stuck open
Fuel level in carburetor float chamber too high
Brown smoke:
Main jet too small
Fuel level in carburetor float chamber too low
Surge tank duct loose
Air cleaner poorly sealed or missing
Handling and/or Stability Unsatisfactory:
Handlebar hard to turn:
Steering stem locknut too tight
Bearing damaged
Steering bearing lubrication inadequate
Steering stem bent
Tire air pressure too low
Handlebar shakes or excessively vibrates:
Tire worn
Swing arm pivot bearing worn
Rim warped, or not balanced
Wheel bearing worn
Handlebar clamp loose
Steering stem head bolt loose
Handlebar pulls to one side:
Frame bent
Wheel misalignment
Swing arm bent or twisted
Steering maladjusted
Front fork bent
Right/left fork oil level uneven
Right/left rear shock absorbers unbalanced
Shock absorption unsatisfactory:
(Too hard)
Front fork oil excessive
Front fork oil viscosity too high
Front fork air pressure too high
Rear shock absorber air pressure too high
Tire air pressure too high
Front fork bent
(Too soft)
Front fork oil insufficient and/or leaking
Front fork oil viscosity too low
Front fork, rear shock absorber spring weak
Rear shock absorber oil leaking
Brake Doesn't Hold:
Disc brake:
Air in the brake line
Pad or disc worn
Brake fluid leak
Disc warped
Contaminated pad
Brake fluid deteriorated
Primary or secondary cup damaged
Master cylinder scratched inside
Drum brake:
Brake maladjusted
Brake linings or drum worn
Overheated
Water in brake drum
.Brake cam, camshaft worn
Oil on brake linings
Battery Discharged:
Battery faulty (e.g., plates sulphated, shorted
through sedimentation, electrolyte level too
low)
Batterly leads making poor contact
Load excessive (e.g., bulb of excessive wattage)
Ignition switch trouble
Regulator/Rectifier trouble
Stator coil open or short
Wiring faulty
Battery Overcharged:
Alternator trouble
Regulator/Rectifier trouble
Battery trouble
Wiring faulty
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