Valve Seat - Replacement

REPLACING VALVE SEAT FOR SERVICE PARTS
1. Bore out old seat until it collapses. Boring should not continue beyond the bottom face of the seat recess in cylinder head. Set the machine depth stop to ensure this.

2. Ream cylinder head recess for service valve seat.

Oversize ...........[0.5 mm (0.020 inch)]:
Intake .............38.500 - 38.516 mm (1.5157 - 1.5164 inch)
Exhaust ..............32.700 - 32.716 mm (1.2874 - 1.2880 inch)

Be sure to ream in circles concentric to the valve guide center. This will enable valve seat to fit correctly.

3. Heat cylinder head to 110 to 130°C (230 to 266°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 to the specified dimensions as shown in SDS.
6. After cutting, lap valve seat with abrasive compound.






7. Check valve seating condition.

Seat face angle "a": 45°
Contacting width "W":
Intake ...............1.09 - 1.31 mm (0.0429 - 0.0516 inch)
Exhaust ...............1.29 - 1.51 mm (0.0508 - 0.0594 inch)






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.

Valve seat resurface limit "L":
Intake ................41.07 - 41.67 mm (1.6169 - 1.6405 inch)
Exhaust ..............41.00 - 41.60 mm (1.6142 - 1.6378 inch)