Topic: Gas Leak From Overflow Tube

[AbbyRider]

Well Crap...I spoke too soon. Still leaking a small amount of gas overnight. Yesterday just to check, I swapped the floats and needles between Carb #1 and #4. Ran the bike for 25 miles. Ran excellent. No leaks. Then this morning #1 is leaking again. I removed the bowl and it was overflowing with gas. So its not the float or needle.
Could it be the needle seat??

The carbs were just rebuilt within the last thousand miles or so. I'm getting frustrated now. Today I decided to disconnect the petcock from the carbs. I hooked up an aux hose from the petcock and closed it off so it wouldn't continue to leak. I'll start the watching and waiting process again. 

Here is my question. Even if the petcock has a small leak, why wouldn't the float shutoff the flow of fuel? I've forgotten the petcock on a time or two and never had an overflow leak. The only sense I can make of the leaky petcock only coming from #1 is that I park the bike on the side stand. So gravity flows down to carb #1.

Thoughts??

It very well could be because of your side stand. Mine does that. I need to shut the gas off and then keep running a little while to use up enough gas that it doesn't all flow down to carb 1. Only happens when your lean is severe enough - usually from increasing rear shock length.

[eigenvector]

+1 on the side stand.  The carbs are all interconnected, so if any of the carbs is leaking it will take the gas from the other carbs PLUS whatever's in the actual fuel line after the petcock. 

You mentioned running it a bit before shutoff, but I think you'd be amazed how little gas that consumes.

I battled problems like this on my CB550 endlessly after stupidly running without a filter.  Small particles of rust caused endless problems on the #1 and #2 carb.

Adjust the float height as good as you can, then drop the float level a bit.  It will run lean, but if that solves your problem you know where to start.  If that doesn't, then you have junk in the lines and need to flush out the debris.

[flybox1]

1 rule out cracks in the stand pipe
2 rule out a poorly sealing bowl drain screw.
3 ensure float height is correct.  test for leaks
4 increase measured float height by 1mm and test for stand pipe leaks.

if you've done all of this, and it still leaks, you'll need (depending on float valve type) new rubber tipped float needles, or new float needle and seat sets.

 If your float valves are operational, they will prevent any leaking, even if your petcock has a leak or you are on your sidestand.

[AbbyRider]

If the angle of the lean is severe enough, the amount of gas in the bowl (even at proper float height) fills it up enough that the drain tube is immersed. I'm talking a fairly good angle though - only happens if you change shock height or some other geometry. It only leaks for a bit though, as the float valve does prevent even more gas getting in.

[lucky]

I think you are right. I removed the bowl and could see very small lines on the brass fitting inside the bowl. I'm guessing this is where it's leaking from? With the bowl off and the petcock closed there wasn't any fuel leaking so I don't think it's the petcock.
So where would I find a replacement float bowl? It's only leaking out of the #1 carb.
Thanks for all the help!

The overflow tube in you float bowl may have a crack. Pull the bowl and fill it with gas to check it. I've had this issue a couple times [different bikes] and just replaced the float bowl.

Clean the overflow tube in the float bowl with fine sandpaper and solder. Do not fill the overflow tube with solder.