YAMAHA Marine F4A Manual De Servicio página 162

POWR
C
B
A
1
2
ROCKER ARM 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.
cC
To prevent chatter marks, turn the valve
seat cutter with an even, downward pres-
sure (4 ~ 5 kg).
Valve seat cutter set:
YM-91043-C/90890-06803
Valve seat lapper:
N.A./90890-06805
9 Refer to the following chart to deter-
mine the appropriate valve seat cut-
ter.
Valve seat area
A
B
C
Valve seat cutting guidelines
1 The valve seat is centred on the valve face,
but is too wide.
Valve seat cutter set
First:
Use 0° cutter
lightly Second:
60° cutter
2 The valve seat is in the middle of the valve
face, but is too narrow.
Valve seat cutter set
Use 45° cutter
5-19
E
Valve cutter
0°
45°
60°
Desired result
To reduce the
valve seat width.
Desired result
To achieve a
uniform valve
seat width.