Yamaha F200B, Service Manual

Page: 325 / 579

7-66
7
b
Previous contact width
5. Adjust the valve seat contact width to
specification using a 45° cutter.
b
Previous contact width
c
Specified contact width
6. Check the valve seat contact area of the
valve. See “Checking the valve seat” (7-
64).
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.
b
Previous contact 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.
b
Previous contact width
• 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.
b
Previous contact width
7. After refacing the valve seat to the speci-
fied contact width, apply a thin, even
layer of lapping compound onto the valve
seat, and then lap the valve using a spe-
cial service tool
1 . NOTICE: Do not get
the lapping compound on the valve
stem and valve guide.
60
b
45
b
c
b
30
60
b
30
b
60
Cylinder head