Valve Seat: Service and Repair

1. If the valve seat width is beyond these specifications, you must grind the seats in order to ensure proper heat dissipation and in order to prevent the build up of carbon on the seats. Use the following procedure:
a. Grind the valve seats with a 46 grinding stone. Use 20 and 65 grinding stones in order to narrow the seat.
b. Narrow the valve seat width to 0.065 mm (0.025 inch) for the intake valve seat and 0.900 mm (0.035 inch) for the exhaust valve seat.
c. When grinding the valves and seats, grind off as little material as possible.
2. If the valve seat widths are acceptable, check the valve seat roundness.
3. The roundness should be within 0.10 mm (0.004 inch) total, as measured with a dial indicator and a solid, slightly tapered pilot which has a slight bind in the valve guide when installed.
4. If the valve seats exceed the roundness specification, grind the valve seats to within 0.05 mm (0.002 inch) indicator reading when new valves are being installed, or if the roundness, seat width, or full contact of the valves is within specification.