1999-2002 TRX400EX Fourtrax Service Manual, Page 112Get this manual
CYLINDERPISTON
TROUBLESHOOTING
Compressiontoo low, hard starting or poor performance at low speed Leaking cylinder head gasket Wornstuck or broken piston ring Worn or damaged cylinder and piston Compressiontoo high, overheating or knocking Excessive carbon built-up on piston head or combustion chamber Excessivesmoke Worn cylinder, piston or piston rings Improper installation of piston rings Scored or scratched piston or cylinder wall Abnormal noise Worn piston pin or piston pin hole Worn connecting rod small end Worn cylinder, piston or piston rings