Page 218 - 2019 SHOP MANUAL CRF1000/A/D

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CYLINDER HEAD/VALVE/CAMSHAFT
SERVICE INFORMATION
CYLINDER HEAD/VALVE/CAMSHAFT
GENERAL
• This section covers service of the valves, rocker arms and camshaft. These services can be done with the engine installed in the
frame.
• When disassembling, mark and store the disassembled parts to ensure that they are reinstalled in their original locations.
• Clean all disassembled parts with cleaning solvent and dry them by blowing them off with compressed air before inspection.
• Rocker arm, valve and camshaft lubricating oil is fed through oil passage in the cylinder head. Clean the oil passages before
assembling cylinder head.
• Be careful not to damage the mating surfaces when removing the cylinder head cover and cylinder head.

TROUBLESHOOTING

• Engine top-end problems usually affect engine performance. These can be diagnosed by a compression test, or by tracing
noises to the top-end with a sounding rod or stethoscope.
• If the performance is poor at low speeds, check for a white smoke in the crankcase breather hose. If the hose is smoky, check
for seized piston ring (page 15-13).
Compression too low, hard starting or poor performance at low speed
• Valves:
– Incorrect valve clearance
– Burned or bent valve
– Incorrect valve timing
– Broken valve spring
– Uneven valve seating
– Valve stuck open
• Cylinder head:
– Leaking or damaged cylinder head gasket
– Loose spark plug
– Warped or cracked cylinder head
• Cylinder/piston problem (page 15-2)
Compression too high, overheating or knocking
• Excessive carbon build-up on piston head or combustion chamber
Excessive smoke
• Worn valve stem or valve guide
• Damaged stem seal
• Cylinder/piston problem (page 15-2)
Excessive noise
• Incorrect valve clearance
• Sticking valve or broken valve spring
• Excessively worn valve seat
• Worn or damaged camshaft
• Worn rocker arm and/or shaft
• Worn rocker arm follower or valve stem end
• Loose or worn cam chain
• Worn or damaged cam chain tensioner
• Worn cam sprocket teeth
• Cylinder/piston problem (page 15-2)
Rough idle
• Low cylinder compression

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