Carb Won't Fill

Dr. Frankenstein · Post by **Dr. Frankenstein** » Mon Apr 17, 2017 5:03 am

Hi All - I'm trying to figure out what would make my carb floats stick to prevent fuel from getting past the pilot jet.

I have a 1964 CA78 all ready to go, but for some reason the fuel will NOT flow into the carb!
Fuel will flow down the line until it gets to the inlet, and stop.

If I take off the bowl, or slightly loosen it by taking off the wire retainer the fuel will drain into the bowl, but put the bowl back on and fuel just backs up in the line.

I have cleaned the carb thoroughly and installed new jets; the floats are measuring 26.5mm from the carb body, the pilot jet needle moves freely in the jet, I have positive fuel flow when the bowl is off...but put the bowl On and "NOPE".

Thinking the floats were hanging up on the bowl, I have tried adjusting them by bending them VERY slightly and gently inward to give them more clearance from the sides of the bowl, tried adjusting the fuel adjustment needle, and the float tang to no avail.

Any ideas?

-John

G-Man · Post by **G-Man** » Mon Apr 17, 2017 7:21 am

John

Have you checked that the gasket isn't swelling up and binding on the float? Some of those gaskets don't like ethanol and behave badly.

Do you have the correct float? Round bowl carbs have floats with the convex part pointing outwards while square bowl carbs have the convex part on the inside.

This is a round-bowl carb from my CB72

Ignore the arrow. That is just pointing to teh float valve.

G

Dr. Frankenstein · Post by **Dr. Frankenstein** » Mon Apr 17, 2017 7:34 am

Hi G-Man - actually I only use non-ethanol gas for my bikes, unless I'm out somewhere and Absolutely have to get gas.

The gasket seems to be okay...it's not puffy or anything...and as far as the shape goes, I'll take a closer look and get back to you.

Is your CB72 carb typically found on the Dreams, or at least that set-up?

jkv357 · Post by **jkv357** » Mon Apr 17, 2017 9:16 am

Dr. Frankenstein wrote:Hi All - I'm trying to figure out what would make my carb floats stick to prevent fuel from getting past the pilot jet.

I have a 1964 CA78 all ready to go, but for some reason the fuel will NOT flow into the carb!
Fuel will flow down the line until it gets to the inlet, and stop.

If I take off the bowl, or slightly loosen it by taking off the wire retainer the fuel will drain into the bowl, but put the bowl back on and fuel just backs up in the line.
(SNIP)

It sure sounds like the float adjustment is off and the float's position is closing the fuel valve when the bowl is in place.

An incorrect float needle (too long) or float valve assembly would do that if the tab on the float was in the correct (or pretty close) position.

Dr. Frankenstein · Post by **Dr. Frankenstein** » Mon Apr 17, 2017 9:26 am

Carb's float level is at 26.5mm, as per manual specs. I double-and triple checked it several times. I think something is hanging up somewhere when I reinstall the bowl, but cannot find the problem.

Dr. Frankenstein · Post by **Dr. Frankenstein** » Mon Apr 17, 2017 9:31 am

Hmmm...although on second thought I DO see what you mean...I'll check that out too.

Luckily I have a complete spare CA77 carb; maybe the previous owner just stuck something in there, although it *looks right...

Dr. Frankenstein · Post by **Dr. Frankenstein** » Mon Apr 17, 2017 9:41 am

But if you change the tab position, you change the float height, right...? I'm starting to lean more towards a bogus needle...

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Carb Won't Fill

Carb Won't Fill

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