TROUBLESHOOTING 3-3
Complaint Symptom and possible causes Remedy
Noisy engine Excessive valve chatter
• Too large valve clearance
• Weakened or broken valve springs
• Worn tappet or cam surface
• Worn and burnt camshaft journal
Noise seems to come from piston
• Worn down piston or cylinder
• Combustion chambers fouled with carbon
• Worn piston pin or piston pin bore
• Worn piston ring or ring groove
Noise seems to come from timing chain
• Stretched cam chain
• Worn sprockets
Noise seems to come from clutch
• Worn splines of countershaft or clutch sleeve hub
• Worn teeth of clutch plates
• Distorted clutch plates, driven and drive
• Worn clutch release bearing
Noise seems to come from crankshaft
• Rattling bearings due to wear
• Worn and burnt big-end bearing
• Worn and burnt journal bearings
Noise seems to come from transmission
• Worn or rubbing gears
• Worn splines
• Worn bearings
Noise seems to come from water pump
• Worn or damaged impeller shaft
• Worn or damaged oil seal
• Contact between pump case and impeller
Adjust
Replace
Replace
Replace
Replace
Clean
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Replace
Engine runs poorly
in high speed range.
Defective engine internal/electrical parts
• Weakened valve springs
• Worn down camshafts
• Valve timing out of adjustment
• Incorrect spark plug gap
• Ignition not advanced sufficiently due to poorly
working timing advance system (Pick-up coil, throt-
tle position sensor and CDI unit)
• Defective ignition coil/plug cap
• Defective magneto
• Clogged air cleaner element
• Clogged fuel hose, resulting in inadequate fuel sup-
ply to carburetor
• Clogged fuel tank vent hose
Replace
Replace
Adjust
Adjust
Replace
Replace
Replace
Clean
Clean and replace
Clean and replace
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