Carter BB-1 Carburetor Diagnosis

Question: The carburetor kit has two check balls. Where do they go?

Two check balls come in the kit, but only one is typically used. It is the ball in the power valve which gets replaced, and it is best removed by inserting a punch or other pin through the holes in the valve body while unscrewing the jet from the bottom. IMPORTANT: a tiny spring goes in between the jet and the ball; don't lose it upon disassembly!

The other two balls in those jets/check valves in the bottom of the bowl are captive and cannot be removed from the assembly. They must, however, be loose or (at the very least) the accel pump won't work. And it is still a good idea to remove those valve assemblies to clean them and beneath them -- if they will come out.

I asked Jeff about making a push up rod for the Carter updraft BB-1. They are not available anymore and the though was that perhaps we could make it ourselves. Here is his answer.

Sorry, no, I don't have the spec on that rod. The diameter is either 3/32" or 1/8" IIRC, and it should be tapered somewhat on the end which goes into the power valve in the bowl bottom.

To determine the right length, take a piece of brass rod and push it down into the power valve to compress the check ball spring. With the spring compressed, mark the rod at the exact point where it is level with the top of the bowl casting gasket surface. Now invert the bowl lid and place the rod into the vacuum piston hole but DO NOT COMPRESS THE PISTON. Mark the exact length from the piston to the bowl lid gasket surface. Measure the two marks on the rod and add the two figures plus 1/32" for the gasket thickness and you should have the length to which to cut the rod.

Float Level
This illustration show how to set the float level on the BB-1 carburetor. The gauge that is shown is not available, but using a metal ruler to do the same measurement is as good as anything.

Intake check ball = 1/8"

Accelerator Pump Stuck - Brass

The brass accelerator pump assembly will come out of the main body when you remove the top of the carburetor, assuming you didn't disconnect the pump lever.

Brass doesn't seem to mix well with cast iron and these pumps tend to get stuck when there is any corrosion going on. When the pump is stuck, apply heat to the outside. They will usually slide out. Worst case, drill a hole from the outside and using a drift punch drive it out. My guess is that if it's this bad, the carburetor is toast. Tap the hole and add a screw or small bolt to plug the hole. Ethanol will eat any epoxy, so try not to use any epoxy, or adhesives.

Check Ball in Pump Well

Some BB-1 carburetors use a check ball at the bottom of the accelerator pump well. This needs to be loose. If not, clean it until it is. A screen over the check ball to keep the dirt out would be great, but not critical.

Carter BB-1 Carburetor Technical

Accelerator Pump Stuck - Brass