Leaky carb... Quick question.

[section8joe]

I'm running 34's and whenever I take the carbs off and re-install them they leak a bunch of gas until I manually shut off the petcock. Once I reopen the petcock everything seems fine. Are my floats too high? Maybe the float valve? Everything seems ok when I take them apart and my floats are set to carb guide specs.

 

[5twins]

I assume this happens when refilling the carbs after they've been emptied? It sounds like the floats are hanging up somehow and sticking open, at least momentarily. Besides the tang for adjusting float level, the BS34 plastic floats also have a stop tab that limits how far they can drop when fuel levels get low .....

Since the float needle is hooked to the tang with a wire loop, it gets pulled out of the seat as the float drops. If the float drops too much, it can pull the needle out too far and it can jamb when trying to go back in. The pic above is of a properly functioning carb set that did not have any overflow problems. Note the angle of the stop tab. It's at not quite 90° to the float frame, angled towards the pivot post slightly.

 

[section8joe]

Do you think I should try to fill the bowls slowly by opening the petcock slowly until the bowls fill up? It's not really a big problem, unless the needle doesn't seat itself. I just wanted to know why this is happening. Thanks Twins!

 

[5twins]

I'm not saying this is the cause, just a possibility. Another might be if you have aftermarket floats. Some of them aren't made as well as originals. Originals have a sleeve inside the pivot and are a nice slip fit on the pivot pin. Many of the aftermarket floats don't have that sleeve and are a loose, sloppy fit on the pin. This can cause all sorts of random leaking and fuel metering problems.

I'm not sure if filling the bowls slowly will help. You can try tapping them with the plastic handle of a screwdriver if they are leaking. Many times that will free things up. Next time you have them off, I would check that stop tab adjustment.