2005-2008 Honda ATV TRX500FA/FGA Fourtrax, Rubicon Factory Service Manual, Page 168Get this manual
CYLINDER HEADVALVECAMSHAFT
CYLINDER COMPRESSION
Warm up the engine to normal operating temperatureStop the engine, disconnect the spark plug cap and remove the spark plug (page 3-9)Install the compression gauge into the spark plug holeShift the transmission in neutralOpen 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 4-7 secondsCOMPRESSION PRESSURE: 608 902 kPa (6.2 9.2 kgfcm2, 88 131 psi) at 450 rpm (min-1) 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 High compression can be caused by: carbon deposits in combustion chamber or on piston head COMPRESSION GAUGE