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14-36
CARBURETOR-BBD
1
' / 2
INCH
VACUUM
,
su
_ "
,--
DIAPHRAGM STEM
PLUNGER) RETRACTED
BY VACUUM
CHOKE DIAPHRAGM
TUBE FITTING
NK621
Fig.
I
I-Measuring the Choke Vacuum Kick Setting
ing the step on the fast idle cam shown in (Fig. lo),
move the choke valve toward the closed position with
light pressure. Insert a NO. 35 drill between the choke
valve and the wall of the air horn.
(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 stop on
the choke shaft, using Tool T109-22 until the correct
valve opening has been obtained. Refer to (Fig. 10).
The choke diaphragm adjustment controls the fuel
delivery while the engine is running. It positions the
choke valve within the air horn by action of the
linkage between the choke shaft and the diaphragm.
The diaphragm must be energized to measure the
vacuum kick adjustment. Use either a distributor test
machine with a vacuum source, or vacuum supplied by
another vehicle.
(1) With the engine
Not
running, open the throt-
tle valves far enough to allow the choke valve to be
moved to the closed position.
(2)
Disconnect the vacuum hose from the dia-
phragm and connect the hose from the vacuum supply,
as shown in (Fig. 11). (A minimum of 10 inches of
mercury (HG) will be required.)
(3) Insert a NO. 11 dFill (Manual Trans.) or a NO. 22
drill (Auto. Trans.) between the choke valve and the
wall of the air horn. Refer to (Fig. 11). Apply suffi-
cient closing pressure on the choke shaft lever to pro-
vide the smallest choke valve opening possible with-
out distortion of the diaphragm link. Note that the
cylindrical stem of the diaphragm will extend as an
internal spring is compressed. This spring must be
fully compressed for proper measurement of the
vacuum kick adjustment.
(4)
An adjustment will be necessary if a slight
drag is not obtained as the drill or gauge is being
removed.
removal of the choke operating link.
The adjustment of this opening will require the
CAUTION: Damage to the diaphragm and the choke
lever slot can result, if the link is not removed for
the bending operation.
(5) Remove the clip and disengage the choke operat-
ing link
from
the diaphragm stem (plunger), then dis-
engage the link from the choke lever. (The best bend-
ing results will be obtained by using a vise and a
pair of pliers.)
(6)
Bend the choke operating link to provide the
correct choke valve opening.
CAUTION: A correction in the length of the link
of
.010
inch, will result in a change of
.010
inch in
the choke valve opening.
As an example, if the choke valve opening is .010
inch in error, the correction in the link length would
be .010 inch.
A 2" micrometer will be helpful in establishing the
original length of the link, as shown in (Fig. 12), be-
fore completing the adjustment.
(7)
Install the choke operating link and recheck
the choke valve opening, using a gauge or drill. Refer
to (Fig. 11).
(8)
Reinstall the vacuum hose to the diaphragm
and with no vacuum applied to the diaphragm,
some clearance should exist between the choke oper-
ating link and the choke lever slot, in both the open
and closed choke valve positions, as shown in (Fig.
13).
This clearance is necessary to allow the choke
valve to close for starting as well as fully open posi-
tion after the engine reaches the normal operating
temperature.
If a clearance does not exist in both of these posi-
tions, a recheck of the operating link adjustment
should be made.
NOTE: Free movement of the choke valve between
the closed and open positions is very necessary.
Fig.
12-Choke
Operating Link Measurements
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