Cylinder Head/Valves Troubleshooting; Compression Too Low, Hard Starting Or Poor Performance At Low Speed; Compression Too High; Excessive Noise - Honda 2004 CRF250X Service Manual

Chain tensioner stopper
Q70MG-0010100
or 07AMG-001A 100 (U.S.A. only)
TROUBLESHOOTING
CYLINDER HEADIVALVES
• Engine top-end problems usually affect engine performance. These problems can be diagnosed by a compression test
or by tracing top-end noise with a sounding rod stethoscope.
• If the performance is poor 8t low speeds, check for white smoke in the crankcase breather hose. If the hose is smoky,
check for a seized piston ring.
Compression too low. hard starting or poor performance at low speed
• Valves:
- Incorrect valve adjustment
- Burned or bent valves
- 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
• Faulty cylinder, piston (page 9-5)
Compression too high
• Excessive carbon build-up in cylinder head or on top of piston
Excessive smoke
• Worn valve stem or valve guide
• Damaged stem seal
• Faulty cylinder, piston (page 9-5)
Excessive noise
• Incorrect valve adjustment
• Sticking valve or broken valve spring
• Worn or damaged camshaft
• Worn or damaged valve lifter
• Worn or loose cam chain
• Worn or damaged cam chain tensioner
• Worn cam sprocket teeth
• Faulty cylinder, piston (page 9-5)
Rough idle
• l ow cyl inder compression
8-5