2006-2012 Honda TRX90 TRX90EX/X Service Manual, Page 110Get this manual
CYLINDER HEADNALVES VALVE SEAT REFACING Follow the refacing manufacturer 's
Valve seat cuttersgrinders or equivalent valve seat refacing equipment are recommended to correct operating ins truc- worn valve seatstions
If the contact area too high on the valve, the seat must be lowered using 30 or 32 flat cutterIf the contact area is too low on th valve, th seat must be raised using 60 interior cutter
CONTACT TOO HIGH
CONTACT TOO LOW
OLD SEAT WIDTH
Re face the sea Wi th 45 seat cut-