Compression too low, hard starting or poor performance at low speed
- Valves
- Incorrect valve adjustment
- Burned or bent valves
- Broken valve spring
- Uneven valve seating
- Valve stuck open
- Cylinder head
- Leaking or damaged cylinder head gasket
- Warped or cracked cylinder head
- Loose spark plug
- Cylinder/piston (section 9)
Compression too high
- Excessive carbon build-up on piston or combustion chamber
Excessive smoke
- Worn valve stem or valve guide
- Damaged stem seal
- Cylinder/piston (section 9)
Excessive noise
- Incorrect valve clearance
- Sticking valve or broken valve spring
- Worn or damaged camshaft
- Worn or damaged rocker arm and/or shaft
- Worn or damaged cam sprocket teeth
- Loose or worn cam chain
- Worn or damaged cam chain tensioner