Honda CRF50F 2004-2015 Service Manual page 81

CYLINDER HEADIV ALVES
TROUBLESHOOTING
• Engine top-end problems usually affect engine performance . These problem can be diagnosed by a compression test or
bV 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 8-5).
Compression too low, hard starting or poor performance at low speed
• Valves:
- Incorrect valve clearance
- Burned or benl valve
- Incorrect valve timing
- Broken valve spring
- Uneven valve seating
• Cylinder head:
- Leaking or damaged head gasket
- Warped or cracked cylinder head
• Worn cylinder, piston or piston rings (page 8· 5)
Compression t oo high. overheating or knocking
• Excessive carbon build-up on pist on crown or on combustion chamber
Excessive smo ke
• Cylinder head:
- Worn valve stem or valve guide
- Damaged stem seal
• Worn cylinder, piston or piston rings (page 8-5)
Excessive noise
• Cylinder head:
- Incorrect valve clearance
- 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 (page 10-7)
- Worn cam sprocket teeth
- Worn rocker arm and/or shaft
• Worn cylinder, piston or piston rings (page 8·5)
Rough idle
• Low cylinder compression
7-5