
Chapter 1 Engine, clutch and gearbox
51
Symptom
Cause
Remedy
Noisy engine
Engine noise
Smoking exhaust
Insufficient power
Overheating
Tappet noise:
Excessive tappet clearance Check and reset.
Weakened or broken valve spring Renew springs.
Knocking noise from cylinder:
Worn piston and cylinder bore Rebore cylinder
fit oversize piston.
Carbon in combustion chamber Decoke engine.
Worn gudgeon
or connecting rod small end Renew.
Excessive run-out of crankshaft
Worn crankshaft bearings
Worn connecting rod
Worn transmission splines
Worn or binding transmission gear teeth
much engine oil
Worn cylinder and piston rings
Worn valve guides
Damaged cylinder
Valve stuck open or incorrect tappet
adjustment
Weak valve springs
Valve timing incorrect
Worn cylinder and piston rings
Poorvalve seatings
Ignition timing incorrect
Defective plug cap
Dirty contact breaker points
Accumulation of carbon on cylinder head
Insufficient oil
Faulty oil
and/or blocked oil passage
Ignition timing too far retarded
Renew.
Renew.
Renew flywheel assembly.
Renew.
Renew gear pinions.
Check oil level and adjust as necessary.
Rebore and fit oversize piston and rings.
Renew.
Renew cylinder barrel and piston.
Renew.
Check and reset.
Rebore
fit oversize piston and rings.
Grind in valves.
Check and adjust.
Fit replacement.
Clean or renew.
Decoke engine.
Refill to specified level.
Strip and clean.
Check
43 Fault diagnosis: clutch
Symptom
Cause
Remedy
Clutch slip
Clutch drag
Worn clutch plates
Engine idle speed too high
Brokensprings
Clutch drum or centre damage
Renew.
Re-adjust.
Renew.
Rectify or renew as required.
44 Fault diagnosis: gearbox
Symptom
Cause
Remedy
Excessive mechanical noise
Difficulty in engaging gears
gear
Kickstarter does not return
Kickstarter slips
jams
Gear change lever does not return
of oil
Broken pinionsorchain
Selector forks or rods bent
Broken springs
gear selector mechanism
Clutch drag
Worn dogs on ends of gear pinions
Worn selectorforks
Broken return spring
Worn ratchet assembly
Broken return spring
Refill.
Renew.
Renew.
Check and renew.
See Preceding Section.
Strip gearbox and renew worn parts.
Renew spring
Dismantle kickstarter assembly and renew
worn parts.
Remove right-hand crankcase cover and
renew spring.