Yamaha F25A Service Manual

5-28
POWR
E
CAMSHAFT AND VALVES
Valve seat refacing
NOTE:
After refacing the valve seat or replacing
the valve and valve guide, lap the valve seat
and valve face.
CAUTION:
To prevent chatter marks, turn the valve
seat cutter while applying an even, down-
ward pressure (4 ~ 5 kg).
● Refer to the following chart to deter-
mine the appropriate valve seat cut-
ter.
Valve seat cutter set:
YM-91043-C/90890-06803
Valve seat area Valve seat cutter
A 90˚
B 45˚
C 30˚
Valve seat cutting guidelines
Å The valve seat is centered on the valve face,
but is too wide.
Valve seat cutter set Desired result
Use
lightly
First:
90˚ cutter
Second:
30˚ cutter
To reduce the
valve seat width.
Å
ı The valve seat is in the middle of the valve
face, but is too narrow.
Valve seat cutter set Desired result
Use 45˚ cutter
To achieve a
uniform valve seat
width.
ı

Yamaha F25A Specifications

General

Brand	Yamaha
Model	F25A
Category	Outboard Motor
Language	English