2006-2014 Honda FourTrax ATV TRX250 EX TRX250X Service Manual, Page 132Get this manual
CYLINDER HEADVALVECAMSHAFT Reface the seat with 45 cutter whenever valve guide is replaced
Use 45 seat cutter to remove any roughness or irregularities from the seat
TOOLS: Seat cutter, 33 mm (45 IN) Seat cutter, 29 mm (45 EX) Cutter holder, 5.5 mm
ROUGHNESS 07780-0010800 07780-0010300 07781-0010101
or equivalent commercially available in U.S.A
Using 32 flat cutter, remove 14 of the existing valve seat material
TOOLS: Flat cutter, 33 mm (32 IN) Flat cutter, 30 mm (32 EX) Cutter holder, 5.5 mm