Refacing The Valve Seat - Yamaha FT50C Service Manual

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 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
62Y5A11
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.
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
4. Use a 60° cutter to adjust the contact
width of the bottom edge of the valve
seat.
Cylinder head
30°
S62Y5460
5-28
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