2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 213Get this manual
CYLINDER HEADVALVE VALVEVALVE GUIDE Check that the valve moves smoothly in the guideCheck the valve for bending, burning or abnormal wearMeasure each valve stem O.Dand record itSERVICE LIMITS: IN: 5.46 mm (0.215 in) EX: '04'05; 5.44 mm (0.214 in) After '05; 4.96 mm (0.195 in)
Ream the guides to remove any carbon build-up before measuring the guideInsert the reamer from the combustion chamber side of the head and always rotate the reamer clockwiseTOOL: Valve guide reamer, 5.5 mm 07984-2000001 or 07984-200000D (U.S.Aonly) 07984-MA60001 or 07984-MA6000D (U.S.Aonly)
After '05; EX: Valve guide reamer, 5.0 mm