1999-2004 Honda TRX400EX FourTrax Service Manual, Page 255Get this manual
TROUBLESHOOTING From page 20-2
10Remove cylinder head cover and inspect lubricationI
Possible cause
Valve train not lubricated properly
Clogged oil passage Clogged oil orifice
Valve train lubricated properly
c 11Check for engine overheating
Not overheating
12Accelerate or run at high speedEngine knocks
- Overheating
Worn piston and cylinder
Excessive carbon build-up in combustion chamber Use of poor quality fuel Clutch slipping Lean fuel mixture
Engine does not knock
Use of poor quality fuel Excessive carbon build-up in combustion chamber Ignition timing too advanced (Faulty ICM) Lean fuel mixture
POOR PERFORMANCE AT LOW AND IDLE SPEED
Possible cause