Valve Seat - Replacement

REPLACING VALVE SEAT FOR SERVICE PARTS






1. Bore out old seat until it collapses. The machine depth stop should be set so that boring cannot continue beyond the bottom face of the seat recess in cylinder head.
2. Ream cylinder head recess.

Reaming bore for service valve seat:
Oversize [0.5 mm (0.020 inch)]:
Intake: 44.500 - 44.516 mm (1.7520 - 1.7526 inch)
Exhaust: 37.500 - 37.516 mm (1.4764 - 1.4770 inch)

Reaming should be done in circles concentric to the valve guide center so that valve seat will have the correct fit.

3. Heat cylinder head to 150 to 160°C (302 to 320°F) by soaking in heated oil.
4. Press fit valve seat until it seats on the bottom.






5. Cut or grind valve seat using suitable tool at the specified dimensions as shown.
6. After cutting, lap valve seat with abrasive compound.






7. Check valve seating condition.






8. Use a depth gauge to measure the distance between the mounting surface of the cylinder head spring seat and the valve stem end. If the distance is shorter than specified, repeat step 5 above to adjust it. If it is longer, replace the valve seat with a new one.

Intake: 44.7 - 44.9 mm (1.760 - 1.768 inch)
Exhaust: 45.4 - 45.6 mm (1.787 - 1.795 inch)