1999-2002 TRX400EX Fourtrax Service Manual, Page 256Get this manual
TROUBLESHOOTING From page 20-2 Possible cause
10Remove cylinder head cover- Valve train not lubricated
and inspect lubrication Valve train lubricated properly properly
Clogged oil passage Clogged oil orifice
11Check for engine overheating- Overheating
Not overheating
Excessive carbon build-up in combustion chamber Use of poor quality fuel Clutch slipping Lean fuel mixture
12Accelerate or run at high speedEngine does not knock
Engine knocks '
Worn piston and cylinder Use of poor quality fuel Excessive carbon build-up in combustion chamber Ignition timing too advanced (FaultyICM) Lean fuel mixture
POOR PERFORMANCE AT LOW AND IDLE SPEED
Possible cause 1Check carburetor pilot screw-Incorrect-adjustment Correct See section 5