2006-2009 Honda TRX250EX/TRX250X Service Manual, Page 126Get this manual
CYLINDER HEADIV ALVECAMSHAFT
TROUBLESHOOTING
Engine top-end problems usually affect engine performa nceThese problems can be diagnosed by com pression testor by tracing top-end noise with sounding rod stethoscope If the performance is poor at low speeds, check for white smoke in the crankcase breather hoseIf he hose is smoky, check for seized piston ring (page 9-5),