Yamaha F2.5A Service Manual page 80

POWR
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.
É
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
4. Use a 60° cutter to adjust the contact
width of the bottom edge of the valve
seat.
5-19
Power unit
S69M5410
30˚
S69M5B00
b Previous contact width
5. Use a 45° cutter to adjust the contact
width of the valve seat to specification.
b
c
b Previous contact width
c Specified contact width
6. If the valve seat contact area is too wide
and situated in the center of the valve
face, use a 30° cutter to cut the top edge
of the valve seat and a 60° cutter to cut
the bottom edge to center the area and
set its width.
b Previous contact width
b
60˚
S69J5890
45˚
S69J5900
69M3E11