reassembling
the
engine. Remember that special tools are available for those
operations. (Refer
to
Chap. 6, "Tools")
2 CYLINDER HEAD AND VALVES
2·1
Retace
of
valve seats
Valve
seat angle
is
45°. After a
rough machining with a
45-degree cut·
ter,
give
perfect fitting. Standard seat
width
is
1.4mm. Excess
in
width affects
airtightness.
If
valve
seat has become
wider,
cut
the
face accordingly with a
c:
cutter with an end angle of 120°.
Use
a
seatT==~~~~~~~~=~'~
cutter of
42tP
in
outer diam. for inlet angle I Valve depression
:E
!
Sopt
facing
valve
seats and of 3:U for exhaust ones.
Valve depression must
be within a range
Fig.
5-1
Valve seat
of
0.8±0.2mm.
In
case
valve
has sunk more than 1mm, which requires a
valve
seat insert
be fitted in, ask your dealer
or
a service shop for the service.
If
valve
face scratched or
worn, replace with a new seat so far as available. It can, however,
be
ground until margin
becomes 1.2mm. .
2·2 How
to
replace valve guides
To
remove valve guide, press it down with remover, while
to
fit
in
a new guide,
use
installer so
as
to
set it with
the
top
end 18mm above the surface
of
cylinder head.
(See
Fig.
5-2)
2-3
Combustion chamber
jet
and director
To
remove combustion chamber jet, lightly press it
out
with a long bolt
of
10tP,
as
illustrated on
the
right.
For new
jet, tap them
in
uniformly until their surfaces get
level
with that of
cylinder head. Setting directions are indicated
in
Fig. 5-4. Having set them right, calk
each
at
a spot with a punch. To replace directors, hammer new ones so
as
to
place jets
midway between inlet and exhaust valves as indicated arrows.
-
70-
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