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CARBURETOR-BBS
14-1 9
(3) Install air horn attaching screws. Tighten
se-
curely.
(4) Install the accelerator pump operating rod and
secure with hairpin clip. Normal operation of the ac-
celerator pump is obtained by installing pump rod in
the center hole of the throttle arm. (On the BBS-
38418 carburetor, be sure the pump rod is in the
short stroke hole of the throttle arm).
Choke Vacuum Diaphragm
Inspect the diaphragm vacuum fitting to insure that
the passage is not plugged with foreign material. Leak
test
the diaphragm to determine if
it
has internal
leaks. To do this, first depress the diaphragm stem.
Then place a finger over the vacuum fitting to seal
the opening. Release the diaphragm stem. If the stem
moves more than
'/I6
inch in ten seconds, the leakage
is excessive and the assembly must be replaced.
Install the diaphragm assembly on the air horn as
follows:
(1)
Assemble to the air horn and tighten the attach-
ing screws securely.
(2) Install the choke operating link in position be-
tween the diaphragm plunger (stem) and the choke
lever. Install the clip to secure.
(3) Inspect the rubber hose for cracks before plac-
ing it on the correct carburetor fitting. Refer to (Fig.
1). Do not connect the vacuum hose to the diaphragm
fitting until after the vacuum kick adjustment has
been made. (See Carburetor Adjustments.)
ADJUSTMENTS
It is very important that the following adjustments
be made on a reconditioned carburetor, and in the
sequence listed:
Accelerator Pump and Bowl Vent
When assembling the accelerator pump to the air
horn, note that the hairpin clip (which opens the
bowl vent) can be placed in any one of three position-
ing notches. These notches correspond to the long,
medium and short pump stroke holes in the throttle
lever. Normally, the bowl vent clip on the pump stem
will be at the middle notch and the pump operating
rod in the medium stroke hole.
The proper procedure is to adjust the amount of
bowl vent opening instead of measuring and setting
the height of the pump plunger.
To check or set the adjustment, proceed as follows:
(1)
Back off the idle speed adjusting screw. Open
the choke valve, so that when the throttle valves are
closed, the fast idle adjusting screw will not contact
the fast idle cam.
(2) Be sure the pump operating rod is in the medi-
um stroke hole in the throttle lever, and that the bowl
vent clip on the pump stem is in the center notch.
BOW
BOWL
VALVE
Fig. 13-Measuring
Bowl Vent Opening
(3) Close the throttle valves tightly.
It
should be
just possible to insert a
'/I6
inch drill
(.060)
between
the bowl vent and the air horn, as shown in (Fig. 13).
If an adjustment is necessary, bend the pump op-
erating rod, using Tool T109-213, at the lower angle,
until the correct bowl vent opening has been ob-
tained.
This is an important adjustment, since too much
lift at the bowl vent will result in considerable loss in
low speed fuel economy.
Remember that if the pump operating rod is moved
to either the short or long stroke position, a corre-
sponding change must be made in the location of the
bowl vent clip, and the amount of lift of the bowl
vent should be retested and adjusted.
The accelerator pump travel is automatically taken
care
of when the bowl vent
is properly adjusted.
Fast Idle Speed and Cam Position
The fast idle engine speed adjustment should be
made on the vehicle, as described in the Fast Idle
Speed Adjustment (On the Vehicle) Paragraph. How-
ever, the fast idle cam position adjustment can be
made on the bench. This adjustment is important to
assure that the speeds of each cam step occur at the
proper time during engine warm-up. Adjust as fol-
lows:
(1)
With the fast idle speed adjusting screw con-
tacting the step on the fast idle cam shown in (Fig.
14), move the choke valve toward the closed position
with light pressure. Insert a drill or gauge between
the choke valve and the wall of the air horn. (Refer to
Specifications for Drill or Gauge Size.)
(2) An adjustment will be necessary if a slight drag
is not obtained as the drill or gauge is being removed.
(3)
If an adjustment is necessary, bend the fast
idle rod at the upper angle, using Tool T109-213, un-
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