2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 77Get this manual
MAINTENANCE DECOMPRESSOR CLEARANCE INSPECTIONADJUSTMENT NOTE: Always inspect and adjust the decompressor clearance after inspecting and adjusting the valve clearance (page 4-10)Rotate the crankshaft clockwise and align the punch mark on the primary drive gear with the index mark on the right crankcase coverMake sure the piston is at TDC (Top Dead Center) on the compression strokeINDEX MARK
Measure the decompressor clearance by inserting feeler gauge between the decompressor arm adjusting screw and right side rocker arm'04'05:
DECOMPRESSOR LIFTER ARM