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ENGINE
FUEL AND EXHAUST SYSTEMS
CARTER CARBURETOR
3-31
When the throttle is opened and fast idle
adjustment screw is lifted from the fast idle
cam, the cam then rotates to bring a lower
point into position for the fast idle adjustment
screw. The engine will then run at a slower
speed at closed
throttle.
d. Choke Operation-Hot Engine
When the engine reaches normal operating
temperature,
the thermostatic coil is heated to
the point where it no longer exerts any spring
te
ns ion on
the
choker valve. The choker valve
is
in
the
wide open position and the fast idle
cam is in the slow idle position so that the fast
idle adjustment screw no longer contacts it at
closed
throttle.
The throttle lever adjustment
screw
then
gov
erns
throttle valve opening at
close
d
throttle.
e
.
Choke Unloader Operation
If
the engine becomes
floodedfor any reason,
t
he
choker
valve can be partially
opened
by
depressing
acc
elerat or pedal to the full extent
of it s
travel. This
causes a tongue or arm on
t
he throttl e lev
er
to contact
and
rotate the fast
idl
e cam,
which forces the choker valve
open.
See
figur e 3-39.
3-23 ADJUSTMENT OF FAST IDLE CAM,
CHOKE UNLOADER, AND FAST
IDLE ADJUSTMENT SCREW
If
the
engi ne ope r at es on fast idle too long
after
starting or else moves to slow idle too
soon , or
the
choke unloader does not
operate
Fig. 3-38-Clearance Between Fast Idle Cam and Boss
properly,
adjust
fast idle cam, choke unloader,
and fast idle adjustment
screw.
1. Remove air cleaner and
silencer.
2. Hold choker valve in closed position and
see that the cam trip lever is in contact with
the fast idle cam, then check the
clearance
be-
tween the arm of fast idle cam and the boss on
throttle body, using feeler gauge .020" thick
and not over
o/t
6"
wide.
See figure 3-38
.
3. If clearance is not .020", slightly loosen
choker lever lock screw, hold
choker
valve closed
and rotate choker lever on shaft until specified
clearance is
obtained.
Tighten lock
screw se-
curely and recheck the clearance.
16"
O
R
NO
.
12
DRILL
CHO KER VALVE
Fig. 3-39-Choke
Unloader
Adju
stment-Carter
4. Open
throttle
unt il the stop on throttle
shaft lever
strikes t
he stop on throttle body,
hold choker valve closed as
far
as possible, then
check the
clearance between
the wall of air
horn and
the
center of upper edge of choker
valve using a
%6"
or
No. 12 drill as a gauge
(.187" to .189" )
.
See figure
3-39.
5. If clearance is not correct, bend the tongue
on
throttle
shaft lever as r
equired
to
provide
a
close
fit of drill
gauge.
6. Start engine and
warm
it up to normal
oper ating
temperature.
Connect
a tachometer
to r
egi st er engine
speed.
7. Remove pin
spring and disconnect the fast
idle
connector r
od f
rom t
h e cam trip lever.
8. While holding the arm of fast idle cam in
contact with boss on throttle body so that the
fast idle adjustment screw bears against the
highest section of cam, turn adjustment screw
to obtain engine speed of 1200 RPM. See figure
3-40.
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