2000-2003 Honda TRX350 Rancher factory service manual, Page 107Get this manual
CYLINDER HEADVALVE
CYLINDER COMPRESSION
Warm up the engine to normal operating temperatureStop the engine, disconnect the spark plug cap and remove the spark plugInstall 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 within secondsCOMPRESSION PRESSURE: 667 kPa (6.8 kgfcm97 psi) at 450 rpm Check that there is no leakage at the gauge connectionLow compression can be caused by: blown cylinder head gasket improper valve adjustment valve leakage worn piston ring or cylinder bent connecting rod High compression can be caused by: carbon deposits in combustion chamber or on piston head