This is driving me mad.
I have had the Standard carb off the bike to try and resolve a overflow problem.
The bike runs fine, but after about 5 miles i have fuel coming out of the overflow pipe.
It seems to happen once the bike gets hot.
I have a rebuild kit, and will replace the float needle.
But......why does it not leak until i am on a journey.
It does not leak when the bike is started.
The carb is clean inside, and the float needle seems to be seating.
I dont wish to switch to a Mikuni or other make.
Is this a back pressure, the engine has been rebuilt recently.
Any help.
Dee.

 

Float level to high? fuel level higher when carb is hot.

 

If you have not replaced the needle yet then do so and make sure the seat is squeeky clean. I had one do something similar and everything looked good, I cleaned it well and checked the level, it still did it once in awhile. Took the needle out again and looked at the edges of the four fingers or guides under a strong glass, they looked like they had a little wear so I polished them with crocas cloth. It seems they were binding on the edges of the carb body and the float boyancy was not always enough to overcome the friction..I know it sounds odd or far fetched but it's be 2 years and 10K miles with no further issues...next time I take the carb apart I'll switch out the needle..

Doug

 

Check your fuel tank vent too, when gas get shaken or warmed (like in the tank going down the road) it can build up pressure and force fuel out of the tank.

 

As an add on to "Miacycles" in a move to troubleshoot this while riding loosen the fuel cap and see if that stops the overflow condition.

If it does you have found your problem. Clean the vent tube with a wire and chase out any insects that have set up residence in there.

 

Float level is often neglected and when the bike is running the fuel level can increase.

 

floats sticking?

 

You're gonna think I'm crazy, but hear me out.
I had a '70 Honda 350 Scrambler and one of the carbs was doing the exact same thing. It drove me crazy. I rebuilt it 7 times and still the same thing. Someone on a vintage bike forum suggested checking the brass overflow pipe in the bowl for a hairline crack. I thought he was full of it, but I was losing my mind rapidly. I checked the pipe and sure enough it had a crack from top to bottom. I cleaned it up real good and roughed it up a bit, then soldered the crack. FIXED!!! Once I got it jetted right, it ran perfect.
It might be a long-shot, but check it anyway.
Parts for them old Honda's are getting hard to find, so soldering seemed like a good option. I also turned my own jets on my metal lathe for that Honda.

 

Thanks Guys, Going to replace the float, and do a carb rebuild at the same time.
It probably does not need the full works, but i have a rebuild kit, so why not.
Writing to HD to get my certificate for removing/replacing a carb.
Thanks again.
Dee.

 

This happened to me. popped the cap loose, rode bout 50 miles, no issues so I bought a new cap & it's not leaking anymore!
Hatch.