2004-2009 Honda TRX450R/TRX450ER Service Manual, Page 217Get this manual
CYLINDER HEADVALVE Using 60 interior cutter, remove 14 of the existing valve seat materialTOOLS: Interior cutter, 37.5 mm (60 IN) Interior cutter, 34 mm (60 EX) Cutter holder, 5.5 mm Cutter holder, 5.0 mm (After '05; EX) 07780-0014100 07780-0014700 07781-0010101 07781-0010400 OLD SEAT WIDTH
or equivalent commercially available in U.S.A60 Using 45 seat cutter, cut the seat to the proper widthVALVE SEAT WIDTH: IN: 1.11.3 mm (0.0430.051 in) EX: 1.31.5 mm (0.0510.059 in) Make sure that all pitting and irregularities are removedSEAT WIDTH
'0405; INTAKEEXHAUST SIDE and After '05; EXHAUST SIDE: After cutting the seat, apply lapping compound and engine oil to the valve face, and lap the valve using light pressureAfter lapping, wash any residual compound off the cylinder head and valveRecheck the seat contact after lappingHAND-LAPPING TOOL