2005-2009 Honda TRX400EX/TRX400X Service Manual, Page 120Get this manual
CYLINDER HEADVALVE
CYLINDER COMPRESSION
Warm the engine to normal operating temperatureStop the eng ineRemove the spark plug (page 4-7) Install the compression gauge with the attachment into the spark plug holeTOOL: Compression gauge attachment 07908-KK60000 or equivalent commerciallyavailable in U.S.AShift the transmission into neutra lPush the choke lever down fully (open )Open the throttle all the way and crank the engine ith the starter motor until the gauge read ing stops risingThe maximum read ing is usually reached withinseconds Th cylm der compressIOn specificarion IS comparatively low because the camshafl has decompressIon device In sta lled