Refacing The Valve Seat - Yamaha F50A Service Manual

POWR
Valve seat contact width a:
Intake: 0.9–1.1 mm (0.035–0.043 in)
Exhaust: 0.9–1.1 mm (0.035–0.043 in)

Refacing the valve seat

1. Reface the valve seat with the valve seat
cutter.
Valve seat cutter set: YM-91043-C
Valve seat cutter holder: 90890-06316
Valve seat cutter:
30° (intake): 90890-06326
30° (exhaust): 90890-06328
45° (intake and exhaust): 90890-06555
60° (intake): 90890-06323
60° (exhaust): 90890-06315
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.
5-43
Power unit
a Slag or rough surface
CAUTION:
Do not over cut the valve seat. Make sure
to turn the cutter evenly downward at a
pressure 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.
b Previous contact width
30°
S62Y5460
62Y3A11