TOHATSU MFS 25D Service Manual page 194

Power Unit
20) Correction of Valve Seat
1. Use a valve seat cutter (commercially available) to correct
the valve seat.
becomes smooth while rotating the cutter in the clockwise
direction.
Be careful not to over-grind the valve seat. Rotate
the valve seat cutter while pressing it down
evenly.
upper end of the valve seat.
lower end of the valve seat.
5-54
30˚ 45˚
a Carbon build-up or uneven surface
b
b Width before correction
b Width before correction
60˚
a
30˚
60˚
4st 25/30 2022