1999-2002 TRX400EX Fourtrax Service Manual, Page 42Get this manual
MAINTENANCE Rotate the crankshaft only counterclockwise to align the mark on the flywheel with the index notch in the left crankcase coverMake sure the piston is mc (Top Dead Center) on the compression strokeThis position can be obtained by confirming that there is slack in the sub-rocker armIf there is no slack, it is because the piston is moving through the exhaust stroke to TDCRotate the crankshaft one full turn counterclockwise and match up the mark againCAUTION:
H the Tmark is passed when try;ng to align it with the index notch, rotate the crankshaft counterclockwise again and align the Tmark with the index notchThis must be done to prevent the one-way decompressor system from functioning and to obtain the correct valve clearance
Check the clearance of all valves by inserting feeler gauge between the adjusting screw and sub-rocker armNOTE: When checking the clearance, slide the feeler gauge from the inside out in the direction of the arrowVALVE CLEARANCES IN: 0.10 mm (0.004 in) EX 0.12 mm (0.005 in) Adjust by loosening the lock nut and turning the adjusting screw until there is slight drag on the feeler gauge