Honda Metropolitan CHF50 Service Manual page 145

CYLINDER HEAD/VALVES
TROUBLESHOOTING
• Engine top-end problems usually affect engine performance. These problem can be diagnosed by a
compression test or by tracing engine noises to the top-end with a sounding rod or stethoscope.
• If the performance is poor at low speeds, check for white smoke in the crankcase breather drain hose.
If the hose is smoky, check for a seized piston ring (page 12-8).
Compression too low, hard starting or poor performance at low speed
• Valves:
- Incorrect valve adjustment
- Burned or bent valve
- Incorrect valve timing
- Broken valve spring
- Uneven valve seating
• Cylinder head:
- Leaking or damaged head gasket
- Warped or cracked cylinder head
- Loose spring plug
• Worn cylinder, piston or piston rings (page 12-8).
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
Worn cylinder, piston or piston rings (page 12-8).
Excessive noise
Incorrect valve adjustment
Sticking valve or broken valve spring
Worn or damaged camshaft
Worn or damaged cam chain
Worn cam sprocket teeth
Worn rocker arm and/or shaft
Worn or damaged cam chain tensioner
Worn cylinder, piston or piston rings (page 12-8)
Rough idle
• Low cylinder compression
8-5