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14-18
CARBURETOR-BBS
WIRE
Fig. 11-Step-up
Piston Wire Free Play
(4) Install the accelerator pump jet, as shown in
(Fig. 7). Tighten securely, using Tool T109-59T. In-
stall a new plug and drive tightly in place.
(5) Install the idle orifice tube, refer to (Fig.
6).
Tighten securely.
(6)
Install the main metering jet and gasket refer
to (Fig. 5). Tighten securely.
(7)
Before installing the step-up piston, be sure the
step-up rod is able to move freely each side of the
vertical position, as shown in (Fig. 11). The step-up
rod must be straight and smooth.
(8) Slide the step-up piston gasket down into posi-
tion in the piston well, then install the step-up piston
spring and step-up piston and rod (Refer to Figure
4).
Install retaining screw and tighten securely. Carefully
guide the step-up rod into the main metering jet. Be
sure the step-up piston slides freely in its cylinder. A
step-up piston stuck in the
UP
position will cause a
rich mixture at part throttle, whereas a piston stuck in
the
DOWN
position will cause a lean mixture at wide
open throttle and poor acceleration.
Measuring the Float Setting
The carburetors are equipped with a synthetic rub-
ber tipped fuel inlet needle. The needle tip is a rub-
ber material which is not affected by gasoline and is
stable over a wide range of temperatures. The tip is
flexible enough to make a good seal on the needle
seat.
The use of the new inlet needle requires a new pro-
cedure in adjusting the float setting. Care should be
taken to perform this operation accurately in order
to secure the best performance and fuel economy.
To correctly set the float height, when the carburet-
or
is being overhauled, proceed as follows:
(1)
Install the floats with the fulcrum pin and pin
retainer in the main body.
(2) Install the needle, seat and gasket in the body
and tighten securely.
(3) Invert the main body
so
that the weight of the
floats
only,
is forcing the needle against the seat.
Hold finger against retainer to fully seat the fulcrum
pin.
(4) Using Tool T109-282
or
T109-220; or a T scale,
check the float, as shown in (Fig. 12). There should be
lI4
or
inch (Taxi) (depending on carburetor, Refer
to Specifications), from the surface of the fuel bowl
to the crown of each float at the center.
If an adjustment is necessary, bend the lip
of
the
float lever either in
or
out until correct setting has
been obtained.
CAUTION: Do not attempt to change the setting
without removing the float, as the synthetic rubber
tip can
be
compressed sufficiently to cause a false
setting which will affect level of fuel in the bowl.
After being compressed, the tip is very slow to re-
cover its original shape. Recheck as described in Step
4 above.
NOTE: It is very important that the float lip
be
per-
pendicular to the needle or slanted not more than
10
degrees away from the needle when the float is
set correctly.
(5)
Place a new gasket on the throttle body and
position the main body making sure they are aligned.
Air Horn
Check the freedom of the choke mechanism in the
air horn. The shaft must float free to operate correct-
(1)
Assemble pump plunger, spring and spring seat
and slide plunger shank through opening in air horn.
Install bowl vent cap over plunger shank, then engage
with pump rocker arm. (On the BBS-3841s carburet-
or, be sure the hairpin clip is in the upper position on
the plunger rod; all others in the middle position.)
(2) Place a new gasket on the main body, then in-
stall air horn by tilting air horn, as shown in (Fig. 3),
in order to engage fast idle link with fast idle cam.
After engaging link, slowly lower air horn and at the
same time guide accelerator plunger into its well.
1 Y
*
GAUGE
TO TOUCH
APPLY PRESSURE TO RETAINER
T O SEAT FULCRUM PIN - S
AT CROWN
L
m
AT GAUGE
?-
-
-?\
MAIN BODY INVERTED
Fig. 12-Measuring
the Float Seffing
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