2006-2014 Honda FourTrax ATV TRX250 EX TRX250X Service Manual, Page 121Get this manual
CYLINDER HEADVALVECAMSHAFT
TROUBLESHOOTING
Engine top-end problems usually affect engine performanceThese problems ca be diagnosed by compression test, or by tracing top-e nd noise with sounding rod or stethoscope If the performance is poor at low speeds, check for white smoke in the crankcase breather hose If the hose is smoky, check for seized piston ring (page 9-5)Compression too low, hard starting or poor performance at low speed ValvesIncorrect valve adjustmentBurned or bent valveIncorrect valve timingWeak valve springUneven valve seatingValve stuck open Cylinder headLeaking or damaged cylinder head gasketWarped or cracked cylinder headLoose spark plug Cylinderp iston problem (page 9-3) Compression too high Excessive carbon build-up on piston head or combustion chamber Excessive smoke Worn valve stem or valve gu ide Damaged stem seal Cylinderp iston problem (page 9-3) Excessive noise Incorrect valve adjustment Sticking va lve or broken valve spring Excessive worn valve seat Worn or damaged camshaft Worn rocker arm andor shaft Worn rocker arm follower and valve stem end Worn cam sprocket teeth Worn cam chain Worn or damaged cam chain tensioner Cylinderpiston problem (page 9-3) Rough idle Low cylinder compression