Sym MB10A7-A series Service Manual page 23

1. General Information
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F. Abnormal Engine Noise
Fault condition
Rocker arm noise
Piston slapping
Cam chain noise
Clutch knocking
Transmission gear noise
1-18
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Possible causes
1. Excessive valve clearance
2. Worn rocker arm
3. Worn camshaft
1. Worn piston and cylinder
2. Carbon deposit in the combustion chamber
3. Worn piston pin or connecting rod lower end
1. Worn camshaft bearings.
2. Worn cam sprocket.
3. Loose or worn cam chain.
1. Excessive clutch plate clearance
1. Worn or deteriorated rear wheel damping rubber.
2. Gear surface worn
3. Worn transmission gear set