Valve Seat

Fig. 20 Checking Sinking Of Valve Set:

1. Inspect contact surface of valve seat and the valve face for roughness or damage. If necessary, resurface valve seat with a 45° valve seat cutter and/or resurface valve face.
2. Apply a thin coat of prussian blue dye marker to valve face.
3. Check valve seating by rotating the valve against the seat. If blue does not appear 360° around valve face, replace valve. If blue dye does not appear 360° around valve seat, resurface valve.
4. Check seat contact width, which should be 0.047 - 0.063 inch (1.2 - 1.6 mm).
5. Check that valve seating position is at center of valve face. If valve seating position is too high, correct with a 75° cutter. If valve seating position is too low, correct with a 35° (IN) cutter or 15° (EX) cutter.
6. Seat valve to valve seat with a lapping compound.
7. Check sinking of valve seat, by measuring protruding length L, Fig. 20. On 1989-91 models, if L is 2.008 - 2.047 inches (51 - 52 mm) for intake valve or 1.969 - 2.008 inches (50 - 51 mm) for exhaust valve, insert a spacer between spring seat and cylinder head to adjust. If L exceeds 2.047 inch (52 mm) for intake valve or 2.008 inches (51 mm) for exhaust valve, replace cylinder head. On 1992 models, dimension L should be between 2.005 - 2.064 inch. If measurement is not as specified, replace cylinder head.