Honda SH125 Manual page 162

CYLINDER HEADIVALVES
TROUBLESHOOTING
0
Engine top-end problems usually affect engine performance. These problem can be diagnosed by a compression test,
or by tracing top-end noise with a sounding rod or stethoscope.
If the performance is poor at low speeds, check for white smoke in the crankcase breather hose. If the hose is smoky,
check for a seized piston ring (page 9-21.
Compression too low, hard starting or poor performance at low speed
Valves:
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Incorrect valve adjustment
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Burned or bent valve
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Incorrect valve timing
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Broken valve spring
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Uneven valve seating
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Valve stuck open
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Leaking or damaged head gasket
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Warped or cracked cylinder head
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Loose spark plug
Cylinder/piston problem (page 9-41.
Compression too high, overheating or knocking
Excessive carbon build-up on piston head or on combustion chamber
Excessive smoke
Worn valve stem or valve guide
Damaged stem seal
Cylinder/piston problem (page 9-4)
Excessive noise
Incorrect valve adjustment
Sticking valve or broken valve spring
Excessive worn valve seat
Worn or damaged camshaft
Worn cam chain
Worn cam sprocket teeth
Worn rocker arm and/or shaft
Worn or damaged cam chain tensioner
Cylinder/piston problem (page 9-41.
Rough idle
Low cylinder compression
Cylinder head:
8-6