Yamaha F400A 2022 - Page 365

Cylinder head
7-65
d. Adjust the bottom edge of the valve
seat contact width using a 60° cutter.
e. Adjust the valve seat contact width to
specification using a 45° cutter.
f. Check the valve seat contact area of
the valve. See “Checking the valve
seat” (7-63).
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, and then cut the bottom edge using a
60° cutter to center the area and set its
width.
• If the valve seat contact area is too narrow
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, and then set
its width using a 45° cutter.
• If the valve seat contact area is too narrow
and situated near the bottom edge of the
valve face, cut the bottom edge of the valve
seat using a 60° cutter to center the area,
and then set its width using a 45° cutter.
2. Lap:
•Valve
a. Previous contact width
a. Previous contact width
a. Previous contact width
b. Specified contact width
30°
a
60°
a
45°
a
b
a. Previous contact width
a. Previous contact width
a. Previous contact width
a
30°
60°
30°
a
60°
a