3
112
E
N
G
IN
E ASS
E
M
B
LY AN
D CO
NTRO
LS
Valve-seat contact conditions: A) Correct; B) Incorrect - contact face damaged-; C) Incorrect - uneven width-.
Positioning of contact area: D) too high; E) too low
Geometric features of valves seats.
Taking the valve out, the paint will be missing in the
contact zone. Its width must not be greater than the
following service limit:
Width service limit of valve seat contact zone: 1,9
mm.
The contact zone can principally take on three different
appearances, as shown in the figure:
A
- correct;
B
- incorrect (contact face damaged);
C
- incorrect (uneven seat width).
Also check the correct positioning of the contact area. It
must be neither higher (case
D
) or lower (case
E
).
Should the incorrect conditions described above occur,
the valve seats must be rectified, respecting the condi
-
tions carried in the following drawing.
If the valve seats are beyond recovery, replace the cylin
-
der head.
A
D
E
B
C
