8.
Valves, Valve
Guides and springs
a
6-
STEM
CAP
spur
COLLAR
sPNNC
INNER SPRING
OUTER
SPRING
F
@B-
spRING~~
VALVE
GUIDE
Wear
on the vahe stems
can
be
seen on examination
and ifa de£inite step has formed, the valves should
be
renewed. Before replacing the valves,
they
must be
ground on to their
seats,
if
good
faces are not formed
with
a
reasonable amount of
grinding.
the
seats
must
be
cut with
a
cutter (included angle
90')
and the valve
refaced
in
a
universal grinder. Do not attempt
to
form
good
seats by an excessive amount of
grinding.
This
will
cause pocketing and restrict the flow of
gases.
If
a
pocket has
already
been
formed this must
be
removed
by
cuttlng with
a
v&e seat cutter larger
in
diameter
than the
vahre head.
Test the valve guides for
wear
by
trying
the fit of
a
new valve
in
them. Both valves shuld
be
quite
free.
but the exhaust valve has more clearance
(.002")
than
Met valve.
To remove the valve guides
fYom the head. two
special tools are required which
can
be
easily
made.
The
ht is a piece of tube with
an
internal
bore of not
less than
7/8".
The second is
a
mandrel about
4"
long
made
fYom
9/
16"
diameter bar
with
the end turned
down to
1/3"
~SSOR~Y
diameter for a
VALVE
L!
length Support of
1/2".
the
CABLE
ADJ
USTINC
SCREW
cylinder head on the
tube
which
fits
over the collar of the
valve guide. Using the mandrel. force the guide out of the
head with a hand press or by using a hammer.
To
fit
a new guide, support the head at the correct angle
and use a hand press and the same mandrel.
If
a hand
press
is
not available, the guide
can
be
replaced using
a
hammer and
a
mandrel,
to
prevent damage to the guide.
Check the length of
the
valve springs which are
oiighml&
2.020
and
2.095
for the inner and outer springs
respectively.
If
these have reached the specified sewice
limits,
they should
be
renewed.
9.
Decompressor
If
the decompressor holds compression and
operates
freely.
there is no need
to
interfere with it except
to
remove
the carbon
fYom the head of the vdve.
If
the valve
is
leaking.
it
will
be
necessary
to
regrind it on its
seat
This
can
be
done without completely dismantling it. Having
disconnected the control cable from
the
handle bar.
unscrew the decompressor from the cylinder head.
Compress the spring and remove the spring cap. Unscrew
the adjusting
screw
and locknut f?om the cable block and
pull the cable sideways out of the block. Push the spring.
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