TOHATSU MFS 8B Service Manual page 134

5. Use 45° degree cutter to adjust contact width of valve seat
to specified value.
6. Valve seat contact area is located on the center, which
should be adjusted to specified value by cutting upper and
lower ends by using 30° degree and 60° degree seat cutters
respectively if the area is too wide.
7. If valve seat contact area is very narrow and is located
nearer to valve face upper end, use 30° degree seat cutter
to cut upper end. If necessary, use 45° degree cutter to
adjust contact width of valve seat to specified value.
8. If valve seat contact area is very narrow and is located
nearer to valve face lower end, use 60° degree seat cutter to
cut lower end. If necessary, use 45° degree cutter to adjust
contact width of valve seat to specified value.
5-30
Contact width before correction
Specified width
Contact width before correction
Contact width before correction
Contact width before correction
4st 8/9.8 2016