1999-2004 Honda TRX400EX FourTrax Service Manual, Page 88Get this manual
CYLINDER HEA WVALVE
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 with the gauge attachment into the spark plug hole
TOOL Compression gauge attachment 07908 KK60000 or equivalent commercially available in -
Shift the transmission in neutral and open the choke lever (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 withinsecondsCOMPRESSION PRESSURE 686883 kPa (7.0 9.0 kgfcm, 100 128 psi)