TOHATSU MFS 25D Service Manual page 195

valve seat to the specified value.
6. If the valve seat contact area is located in the center
and the area is too wide, adjust the contact width to the
specified value by cutting the upper and lower ends using
30° and 60° seat cutters respectively.
7. If the valve seat contact area is too narrow and located
nearer to the valve face upper end, use a 30° seat cutter
to cut the upper end. If necessary, use a 45° seat cutter to
adjust the contact width of the valve seat to the specified
value.
8. If the valve seat contact area is too narrow and located
nearer to the valve face lower end, use a 60° seat cutter
to cut the lower end. If necessary, use a 45° seat cutter to
adjust the contact width of the valve seat to the specified
value.
4st 25/30 2022
c of the
b Width before correction
c Specified width
30˚
b Width before correction
30˚
b Width before correction
b Width before correction
b
c
45˚
60˚
b
60˚
5
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