1986-1987 Honda TRX350 FourTrax 4X4, 1987-1989 TRX350D Foreman 4X4 Service Manual, Page 78Get this manual
CYLINDER HEADIVALVES VALVE SEAT REFAC ING (1) ROUGHNESS Use 45 degree cutter to remove any roughness or irregularities from the seatNOTE Reface the seat with 45 degree cutter whenever valve guide is replaced
Use 32 degree cutter to remove the top 14 of the existing valve seat material
Use 60 degree cutter to remove the bottom 14 of the old seatRemove the cutter and inspect the area you have refaced