Correction Of Valve Seat - TOHATSU MFS 9.9 Owner's Manual

Power Unit

16) Correction of Valve Seat

1. Use valve seat cutter (commercially available item) to correct
valve seat.
Be careful not to over-cut valve seat. Turn valve
seat cutter while pushing down evenly.
2. Turn 45° degree cutter clockwise to cut valve seat surface to
make it smooth.
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.
5-32
30˚ 45˚
45˚
aCarbon or uneven surface
b
bContact width before correction
bContact width before correction
60˚
a
30˚
b
60˚
4st 9.9/15/20 2008