2006 Honda TRX680 Rincon Factory Service Manual, Page 208Get 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 4-7)Install the compression gauge into the spark plug holeTOOLS: Compression tester Adaptor EEPV303A MT26J200 COMPRESSION GAUGE
Shift 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 withinsecondsCOMPRESSION PRESSURE: 510 kPa (5.2 kgfcm2, 74 psi) at 390 rpm (min1) 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 carbon deposits in combustion chamber or on piston head