Carter BB Updraft Carburetor

Carter B&B Updraft Carburetor Rebuild

Dissassemble Carburetor

  • Remove screws which hold upper body and lower body.
  • Lift off the upper body and pump assembly.
  • Unscrew float hinge pin and lift out float and float needle.
  • Remove main jet inlet valve, pump, check valve and economizer valve assembly
  • Remove the main discharge nozzle.
  • Remove vent tube.
  • Remove step up piston plug, piston and spring.
  • Remove idle passage tube.


  • Soak parts overnight in a bucket of carburetor clean (any parts store brand)
  • Wash with hot water to remove all chemicals.
  • Blow out all passages with compressed air.
  • Pay special attention to the step up rod parts. This must operate freely.
  • Using thin wire clean out the ethanol residue left in the carburetor. Be careful not to enlarge the holes.
  • Test the float by immersing in hot water. As the inside of the float heats up and expands, any hole will show up with bubbles.

Ready for your Carter B&B updraft carburetor kit.


  • Reverse the disassembly instructions.
  • The pin end of the economizer piston rod should be inserted in the economizer valve assembly.



A customer is working on a B&B updraft carburetor. We supplied a kit which does not have the 2 gaskets that go on the venturi. The parts are illustrated in the photo attached. #15 venturi gasket upper & #47 venturi gasket lower.

I’m not sure these gaskets are really needed anymore. What do you think?


In a word:  no.  In 20+ years of restoring BB updrafts I have never even seen those gaskets in a BB, much less replaced them.  In some updraft carbs they are critical, but evidently not in this one.

Recent Posts

Choke Types

We have 4 different types of chokes, Intregal, Divorced, Electric & Electric Conversion.

Intregal Choke

Integral ChokeThe integral choke is mounted on the carburetor, either near the top, or near the bottom. The illustration shows the choke mounted on the top of the carburetor. The thermostat is heated by a heat tube that runs down to the exhaust manifold. The heat tubes heats up the thermostat and moves the choke valve to the open position. A vacuum passage in the carburetor feeds up to the choke housing and helps pull in the heat from the heat tube. Some of these chokes will also have a hot water jacket running through, or on the thermostat to facilitate heating.

Divorced Choke

Divorced ChokeThe divorced choke typs has the thermostat mounted in the intake manifold instead of on the carburetor. In this illustration, the arrow points to the thermostat which is covered by a metal shield. A rod connects the thermostat to the choke lever, which controls the choke valve to be opened, or closed. As the intake manifold heats up, the thermostat mounted, expands, opening the choke valve.


Electric Choke


Electric ChokeThis is a typical electric choke mounted on the carburetor, which is integral. In this case there is one wire on the choke thermostat. This is the 12v source, which all electric chokes use. The thermostat is grounded via the carburetor itself. Some electric chokes will have a 2nd wire (ground wire), which is connected back to the carburetor. When the key is on the thermostat is heated up, opening the choke valve.

Electric Choke Conversion


Electric Choke ConversionThis is a typical electric choke conversion kit. This is used to convert an integral, or a divorced choke to an electric choke. These choke kits come with a temperature sensor that bolts on to the intake manifold, which provides more accurate choke control than with an electric choke without the gauge. The electric choke conversion kit is not used for a manual choke conversion. The choke housing must be in place in order for it to work.
This choke installs in 20 minutes or less with no special
tools. Remove the old choke thermostat and replace with this choke conversion kit.
Attach the temperature sensor under an existing engine bolt.
Wire the positive wire into the vehicles electrical system. Ground the choke to the carburetor.
Complete instructions are provided for each application.


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