Yamaha MM700A Manual page 61

TROUBLESHOOTING
Plnging
Abnormal noise during engine
idle with a cold engine
Abnormal noise during cruising
Abnormal noise during
sudden acceleration
ABNORMAL ENGINE NOISE
t
Check:
*Faulty ignition system component
Incorrect spark plug heat range
Execessive carbon buildup in
combustion chamber
*Incorrect fuel/oil mixture ratio
*Poor quality fuel
Check:
Excessive piston clearance
Excessive piston ring wear
Excessive piston skirt wear
*Bent or damaged connecting rod
Check:
Stuck piston ring
Damaged piston ring
Worn main engine bearing
*Piston scuffing or light seizure
Check:
Excessive piston pin clearance
Excessive clearance at the connecting
rod upper end
Excessive clearance at the connecting
rod lower end
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