Turned on gas and both Bings spouted gas from vent holes behind little black plastic Bing plates, just above float bowl. What could be cause and how to fix?
Thanks loads in advance!
For fuel to get that high above the float bowls, the floats are not pushing the needle into the seat to disrupt the fuel flow. Also, the fuel is probably entering the throat of the carburetor and draining into the motor. I would imagine that the float and float needle is bound up or the float is no longer floating.
former Airmarshal, IL.
@8053 Thanks. I'll check.
To check for trash that may be fouling the float valve do this....
1) Turn OFF the fuel.
2) Pop the float bowls off one at a time.
3) Pour the contents of each float bowl through a common white kitchen paper towel. The gasoline will easily pass through the towel, but any trash will remain AND BECOME VERY EASY TO SEE against the white background. Any water present will also "bead up" on the paper towel. Any trash is cause for concern.
4) Now carefully pull the float pin and drop the float and float needle from both carb bodies.
5) Place a while kitchen towel under the carb and turn the fuel back on for about 2 seconds. This will wash any trash out of the float seat, and again onto the paper towel where it can be easily seen.
It is common for older Airhead fuel tanks to 1) lose their anti-rust coating and/or start to rust. Bright Orange-Red is flakes of the anti-rust paint coating, dark Brown particles are rust from inside the tank. Black specs will be pieces of "rubber" from very old fuel line or the seals inside the petcocks.
What you are looking for is not big pieces, but tiny dark specs about 1/3 the size of a grain of beach sand. It doesn't take much to upset the delicate float needles.
> If you haven't done so already, then order the "new" updated ethanol-proof floats, float needles and float bowl gaskets from Bing.
> ANY new fuel line you fit must be marked "SAE J30" or don't buy it. This line will resist rotting and breaking off caused by exposure to ethanol fuels.
> It's difficult and expensive to have your fuel tank coated, so the better way may be to add fuel filters above each carb. Owing to the limited space on an Airhead, fitting even the smallest filter can be difficult. If you are installing all new fuel lines, then routing the lines in a non-standard method may give you the extra room you need. Consider a layout that has the cross-over run around the rear of the engine (as opposed to under the air box)...
(If your petcocks have the fuel line come straight down, rather than out the rear. Consider replacement petcocks.)
Hope this helps.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
@wobbly Thanks for all this input. I'm having a similar carb leak issue on my recently acquired R90/6. You suggest pulling the float pins/floats/needles... is that possible while the carbs are still on the bike?
THX...
-craig
Wobbly might have a different answer but, I would believe that dealing with the float hinge pins would be difficult or impossible with the carbs on the bike. I just installed new floats, pins, and needle valves in my 40mm Bings. I took them off the bike. The pin can only go out and in one direction. It has one serrated end, that anchors it in the cast post that is part of the carb. You have to look very closely. That serrated end is like a head on the pin. The pin needs to come out head first, and be reinstalled as it was. I gently tap it out with a very small pin punch. Being careful is key - you don’t want to break the cast post on the carb.
To remove the carbs - I disconnect the choke by undoing the 11mm nut and removing the little arm, along with undoing the choke cable from the boss on the carb top. Unhook the end of the throttle cable from the throttle arm. Then I remove the carb top and leave the throttle cable attached to it. That way I don’t lose my carb synchronization. Of course then I remove the carb piston and diaphragm. This way, also, the carb will sit flat on the bench upside down - easier to work on.
@4949 Thanks...
@wobbly Thanks for all this input. I'm having a similar carb leak issue on my recently acquired R90/6. You suggest pulling the float pins/floats/needles... is that possible while the carbs are still on the bike?
Craig -
Sorry for the delayed response. To answer... pulling the pins and dropping the floats CAN be done with the carbs in-situ.
But what is the object of the exercise ? The object is not simply "a fast way to remove the float".
The object is to capture any tiny pieces of trash so that you have firm evidence, so that you can know without a doubt, that the remedy you are pursuing is the REAL cause, and that all your efforts will be EFFECTIVE.
But, I'm not saying the 2 things are mutually exclusive either. If you can figure out a way to leave the carb in-place and capture all the fuel line trash in (say for instance) a white, conical coffee filter held under the carb the entire time you are swapping out the old float parts for the new float parts, then go for it.
But I would also remind you that this process would require you to clean the outside of the carb before starting, because you'll never be able to distinguish between trash from the carb's outside from trash from the carb's inside. Remembering that what you are searching for is trash about the size of the "period" at the end of this sentence. 😮
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
@wobbly Thanks... My issue seems to be causing me a bit of confusion. I drained my tank, cleaned the petcocks, added new screens. Tank does not look bad at all and there was very little in the way of anything other than fuel in it. No sludge, grit, etc.
After that...I did the remove the bowl again, turned on the fuel, did the jiggle-the-float routine and if I gently pushed up on the floats, the fuel shut off. I put it back together, fired it up, no leaking carb. Took it out for a ride...and just like the first time it was an issue, got to about 3 miles from home and the carb started peeing fuel again. The intermittent nature of this makes me think it's something besides some grit/dirt...but not sure.
So, probably going to have to dig into it a bit more.
Thanks for getting back to me...
The intermittent nature of this makes me think it's something besides some grit/dirt...but not sure.
So, probably going to have to dig into it a bit more.
Step 2: Check the float level on both sides.
Owning an old Airhead is easy.
Keeping an old Airhead running great is the true test.
Hello again, Phil. Just to share - many years ago I had installed some less expensive aftermarket floats, along with new needles and those tiny wire hairpins. All was well adjusted, but I had an intermittent issue with one carb wanting to either starve or flood. I never could pin down what was happening. With the bowl removed, everything worked fine. However, with the bowl in place and in normal operation, apparently the float could somehow stick or bind. I suspect that the fit between the float arm and the pivot pin was not what it should be, or the hairpin was somehow creating a bind, but really can’t say for sure. I just got frustrated and purchased new genuine floats and tiny hairpins - no more troubles.
Thanks for the ideas... I'll take a closer look. I'm still baffled by the fact that they don't always leak. After the bike has been sitting some, I can fire it up with no issues...and usually get a couple miles down the road before it starts over flowing.
...anywho... thanks for the ideas on things to look for.
-craig
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