Refacing The Valve Seat - Yamaha F30A Service Manual

POWR
4. Determine the valve seat contact width
a by measuring the blueing dye marking
on the valve face. Reface the valve seat
if the valve is not seated properly or if the
valve seat contact width is out of specifi-
cation. Check the valve guide if the valve
seat contact width is uneven.
Valve seat contact width a:
Intake and exhaust:
0.9–1.1 mm (0.035–0.043 in)

Refacing the valve seat

1. Reface the valve seat with valve seat
cutters.
5-33
Power unit
S68V5720
Valve seat cutter holder:
90890-06316
Valve seat cutter:
30° (intake): 90890-06327
30° (exhaust): 90890-06328
45° (intake): 90890-06325
45° (exhaust): 90890-06312
60° (intake and exhaust):
90890-06323
2. Cut the surface of the valve seat with a
45° cutter by turning the cutter clockwise
until the valve seat face has become
smooth.
45˚
a Slag or rough surface
CAUTION:
Do not over cut the valve seat. Be sure to
turn the cutter evenly downward at a pres-
sure of 40–50 N (4–5 kgf, 8.8–11 lbf) to
prevent chatter marks.
3. Use a 30° cutter to adjust the contact
width of the top edge of the valve seat.
S67C5090
a
S6AG5J20J
67C3K11