Frustrating fuel leak out of Left Float bowl overflow

Saulmac

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Hi, I have been having a constant and nagging issue with my 1978 special. Fuel dribbles out of the overflow on the left float bowl. It does this persistantly when the bike is idiling or turned off and on the stand.
Now it all started when a 'mechanic' gave me the bike back after he had done a carberator rebuild for me. I had attempted to clean them myself but ran into some problems that were outta my ameatuer league. I gave the mechanic the carbs back again when the leak started. He said he adjusted the float bowl height. Didn't work. Was sick of him so have tried to fix the problem myself.
Since the carb rebuild I took off the carbs and put in new needle jets, float valve seats and needle O-rings. The leak continued.
So I bought brand new petcocks to replace the vacuum ones. Thought this would surely solve my problem. Nah, still leaks. Have ran into a concrete wall with this and would appreciate some advice.
Can anyone help?
Thanks
 
Just to be sure of them dip the floats in a cup of hot water, watch for bubbles. Many of these old floats have cracks and leak gas. Float height setting is important also. Metric 90 degree grease fittings with the ball drilled out and a little clear tubing allow you to make a sight gauge to see where the gas level REALLY is.
 
if your carbs have the overflow outlet fittings on the bottoms of the bowls look very carefully at the brass stand tube inside the bowl, if cracked float level new needle/seat ect. won't fix it as the leak is below shut off level, the fuel tries to refill as the bowl drains
 

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If you really do have '78 carbs then there will be no overflow nipple on the bowl bottoms and no stand pipe inside the bowls. Those parts were eliminated starting with the '78 carbs. If you have those parts then either the bowls or maybe even the entire carb set is from an earlier model. If you positively I.D. the carb set, it will make it easier to tune them and solve problems with them. Post some pics of your carbs and maybe we can identify the year.
 
Some good advice, thanks.
The carbs are not 78's your right. They are 76-77's I beleive. This bike has a long history, but a relatively short one with me. From what I have gathered the engine is not the original, nor are the carbs. She is far from stock issue.
The amount of money I have spent on the fuel system I could have easily bought new carbs off of mikesxs. But now I feel that I am too deep in now to throw that money away and buy new ones.
I'm off to pull the carbs again and inspect those floats with a magnifying glass.
Attached a photo of the SOBs
 

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Pulled the floats out and the float from the left carb had what I can only conclude is gas in it. Must have a very small leak, the thing looks pretty beat up. Dunked it in warm water, but very hard to tell if there was bubblles coming out of it. So I'm gona order two new ones and fingers crossed this solves the issue.
Cheers
 
Did you ever get this issue solved? I'm having the same trouble and I've done essentially the same repairs that you have. Still having the issue. Plastic floats. Both brand new now. Rebuilt petcock too. Bike was fine all weekend and then this morning it was flooded again.
 
littlebill31 i swear, my carb guide has coffee and whiskey stains on it. In fact, I have the PDF file on my phone now that I read through kindle. SO glad I have that option haha. That thing has helped me so much through all of this. I guess tonight I will go through it again. Thanks for the reminder.
 
Runaway; you have BS34's and you have replaced the float valve o-rings?
Float heights set correctly for plastic floats.
If your gas tank is shedding fine rust a float leak will happen, the rust will sometimes get stuck in the valve.
New MikesXS plastic floats?????
 
Yes I have replaced them. I didn't at first because the old ones looked/look just fine, but i went ahead and did that since i was still having issues. The floats are from mikes and they are both set right where they should be. I have checked and rechecked that a few times. My tank doesnt look rusty, but I am beginning to think that I'm gettting some gunk.

Check this out. Since I have been working on my bike my gas is always pretty low and I've put in about a gallon of gas at work twice now because I've run out of fuel. BOTH times it has caused the flooding issue. It didn't click until about an hour ago... but could that be the issue? maybe that gas isn't good? (for the bike at least) We use it for cars.

That could also be preventing the petcock diaphragm from fully closing as well right? If so then I think that's what it is.

Oh, and yes sir they are the BS34's.
 
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