2005-2006 Honda ATV TRX500FE/FM/TM FourTrax Foreman Factory Service Manual, Page 133Get this manual
CYLINDER HEADVALVE
CYLINDER COMPRESSION
Warm up the temperatureengine to normal operating COMPRESSION GAUGE Stop the engine and remove the spark plug (page 4-9)Install the compression gauge into the spark plug holeShift the transmission in neutral and close the choke knob (OFF)Open the throttle all the way and crank the engine with the starter motor until the gauge reading stops risingThe maximum reading is usually reached withinsecondsThe cylinder compression specification is comparatively low because the camshaft has decompression device installed
COMPRESSION PRESSURE: 440 kPa (4.5 kgfcm2, 64 psi) at 380 rpm (min1) Check that there is no leakage at the gauge connectionLow compression can be caused by:blown cylinder head gasketimproper valve adjustmentvalve leakageworn piston ring or cylinder High compression can be caused by:carbon deposits in combustion chamber or on piston head