Originally Posted by Stadger
It sounds like you're more of a mechanic than you think. You've already got the problem diagnosed. Take the float bowl off the bad side carb and put the fuel line that goes to it in your mouth. Blow through the line while lifting and lowering the float gently. When the float is down you should be able to blow through the line and when raised you should not. It sounds like the fuel inlet or float needle valve on that carb is plugged. If that's the case, remove the float and the little needle valve and shoot some carb cleaner throught the fuel inlet. You may need to do this several times and even possibly use compressed air. That should take care of the problem for now. Those old carburetors were strictly gravity-fed and require no vacuum or anything to fill the float bowl. They are simple to rebuild if you just take your time and do one at a time. I sure would like to hear if you get it running right. Another thing, the ethanol in today's fuel is hell on carburetors. It plugs them up in a matter of days. If you can get non-ethanol gas, use it.
I'm still not a mechanic, lol, I've just worked on this bike way too many times. Actually my mechanic buddy tells me if I ever get to work on a simpler engine I'll be pretty good. This engine has even stumped him a few times, and he's built drag bikes for years. I'll try that trick you suggested, I have a length of new fuel line I can use.
I've cleaned the carbs several times, I removed the float needle valve assembly and used a small straight pick to make sure the inlet was clear and it is. I reinstalled the entire float assembly and the float needle valve rises freely during visual inspection off the bike.
In the float needle valve, there is a small spring loaded tip that the float itself hits, this is inside the larger valve. I might have to take a photo because its hard to describe. The valve itself is like 1/4" diameter 1" long, this small tip I'm talking about looks like a bic pen tip and is opposite the end that seals the larger valve. Is this an orifice that needs cleaned, or is it just to pad the float itself? I don't see where it goes all the way through. Any clue on that?
The other thing that bothers me is I have a single petcock (which doesn't dump fuel as fast as I think it should, so I'll clean that out). The fuel line exits that and goes to the rear of the engine and then I have it T'd to the carbs . It's clear fuel line and it's got a big air bubble in it (even with the gas cap off). What would cause that bubble to not be able to exit? There is a low spot but I can push it down so there is a constant downward flow available, and I remember from science class that as long as the other end is lower, it should flow freely to the bottom.