Yamaha F30B 2018 Service Manual page 193

a. Previous contact width
d. Adjust the valve seat contact width to
specification using a 45 cutter.
a. Previous contact width
b. Specified contact width
e. Check the valve seat contact area of the
valve. See "Checking the valve seat" (7-
36).
Example:
• If the valve seat contact area is too wide
and situated in the center of the valve
face, cut the top edge of the valve seat
using a 30 cutter. Cut the bottom edge
using a 60 cutter to center the area and
set its width.
30°
a. Previous contact width
a
b
45 °
a
60°
• If the valve seat contact area is too nar-
row and situated near the top edge of the
valve face, cut the top edge of the valve
seat using a 30 cutter to center the area.
Set its width using a 45 cutter.
30°
a. Previous contact width
• If the valve seat contact area is too nar-
row and situated near the bottom edge of
the valve face, cut the bottom edge of the
valve seat using a 60 cutter. Set its
width using a 45 cutter.
a. Previous contact width
7-38
Camshaft and valve
a
a
60°