Refacing The Valve Seat - Yamaha F80B Service Manual

Valve seat contact width a:
1.20–1.60 mm (0.0472–0.0630 in)

Refacing the valve seat

1. Reface the valve seat with the valve seat
cutters.
Valve seat cutter holder:
90890-06553
Valve seat cutter:
30° (intake): 90890-06326
30° (exhaust): 90890-06328
45° (intake): 90890-06555
45° (exhaust): 90890-06312
60° (intake): 90890-06324
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.
6D93G11
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.
b
b Previous contact width
Cylinder head
1
2
S63P5240
3
4
5
6
7
8
30˚
S69J5880
9
5-30