Honda NC700 2012 Service Manual page 311

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CYLINDER HEAD/VALVES
TROUBLESHOOTING
• Engine top-end problems usually affect engine performance. These problems can be diagnosed by a compression test or by
tracing engine noises to the top-end with a sounding rod 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 15-16).
Compression too low, hard starting or poor performance at low speed
• Valves:
– Incorrect valve clearance adjustment
– Burned or bent valve
– Incorrect valve timing
– Broken valve spring
– Uneven valve seating
• Cylinder head:
– Leaking or damaged cylinder head gasket
– Warped or cracked cylinder head
– Loose spark plug
• Worn cylinder, piston or piston rings (page 15-16)
Compression too high, overheating or knocking
• Excessive carbon build-up on piston crown or on combustion chamber
Excessive smoke
• Cylinder head:
– Worn valve stem or valve guide
– Damaged stem seal
• Worn cylinder, piston or piston rings (page 15-16)
Excessive noise
• Cylinder head:
– Incorrect valve clearance adjustment
– Sticking valve or broken valve spring
– Damaged or worn camshaft
– Loose or worn cam chain
– Worn or damaged cam chain
– Worn or damaged cam chain tensioner
– Worn cam sprocket teeth
– Worn rocker arm and/or shaft
– Worn rocker arm and valve stem end
• Worn cylinder, piston or piston rings (page 15-16)
Rough idle
• Low cylinder compression
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