Yamaha F150A Service Manual page 269

30 45
Valve seat cutter holder: 90890-06316
Intake:
Valve seat cutter 30°: 90890-06327
Valve seat cutter 45°: 90890-06325
Valve seat cutter 60°: 90890-06324
Exhaust:
Valve seat cutter 30°: 90890-06326
Valve seat cutter 45°: 90890-06325
Valve seat cutter 60°: 90890-06324
2. Cut the surface of the valve seat using a
45° cutter by turning the cutter clockwise
until the valve seat face has become
smooth.
Do not overcut the valve seat. To prevent
chatter marks, make sure to turn the cut-
ter evenly using a downward force of
40–50 N (4.0–5.0 kgf, 8.8–11.0 lbf).
45 ˚
60
a
7-44
a. Slag or rough surface
3. Adjust the top edge of the valve seat con-
tact width using a 30° cutter.
30˚
a. Previous contact width
4. Adjust the bottom edge of the valve seat
contact width using a 60° cutter.
a. Previous contact width
5. Adjust the valve seat contact width to
specification using a 45° cutter.
a. Previous contact width
b. Specified contact width
6. Check the valve seat contact area of the
valve. See "Checking the valve seat" (7-
43).
Cylinder head
a
a
60 ˚
a
b
45˚