2006-2012 Honda TRX90 TRX90EX/X Service Manual, Page 111Get this manual
CYLINDER HEADVALVES Use 60 interior cutter to remove the bottom 14 of the old seatRemove the cutter and inspect the area you have refacedOLD SEAT WIDTH
TOOLS: Interior cutter, 22 mm (60 INEX)077800014202 Cutter holder, 5.0 mm 07781-0010400 or equivalent commercially available in U.S.AUsing 45 seat cutter, cut the seat to the proper widthMake sure that all pitti ng and irregularities are removedRefinish if necessary