Yamaha F40BED, Service Manual

Page: 238 / 537

POWR
5-35
CYLINDER HEAD
E
Refacement steps
A
Valve seat is centered on valve face but
is too wide.
B
Valve seat is in the middle of the valve
face but is too narrow.
C
Valve seat is too narrow and is near
valve margin.
D Valve seat is too narrow and it is
located near the bottom edge of the
valve face.
A
B
C
A
B
Valve seat cutter set
YM-91043-C/90890-06803
Cut section as follows
Section Cutter
A 90°
B 45°
C 30°
Valve seat cutter set Desired result
Use
lightly
90° cutter To reduce valve seat
width.
30° cutter
Valve seat cutter set Desired result
Use 45° cutter
To achieve a uniform
valve seat width.
C
Valve seat cutter set Desired result
Use
90° cutter To center the seat
and set its width.
45° cutter
D
Valve seat cutter set Desired result
Use
30° cutter To center the seat
and increase its
width.
45° cutter