Correction Of Valve Seat - TOHATSU MFS25 Service Manual

13) Correction of Valve Seat

1. Use valve seat cutter (commercially available item) to correct
valve seat.
2. Turn 45 degree cutter clockwise to cut valve seat surface to
make it smooth.
Be careful not to over-cut valve seat. Turn valve
seat cutter while pushing down evenly.
3. Use 30 degree cutter to adjust contact position of valve seat
upper end.
4. Use 60 degree cutter to adjust contact position of valve seat
lower end.
25/30 2006
0û
45û
5û
a Carbon build-up or uneven surface.
b
b Width before correction
b Width before correction
60û
5
a
30˚
b
60˚
5-35