Topic: Fuel leaing out of the bottom of one of my carbs on my 1970 cb750

[cb750tom]

Hi All,

I am new to this forum and have never done this before, but lets give it a try.  I just bought a 1970 Cb750 that is in really good shape, but unfortunately it was sitting around for a few years without running.  I have just ripped apart the carbs and put them back together and just took it on a test ride. It was idling high and when I got back fuel was streaming out the bottom of one of the carbs. 

Thanks for any ideas as to why this happening.

[azuredesign]

Remove the float bowl, check the gasket. Also check that the float is pushing it's jet, which is removable if you remove the float, into it's seat. I've also seen main jets floating in the bowl when the bowl is removed, so removing the bowl from the offending carb is probably a good first step. Good luck!

[Johnie]

Yes, another gold.  Looks nice in the avatar.  Fuel must be coming out the overflow tube which exits at the bottom of the bowl.  I had the same issue on my KO and changed all the float needles and seats.  Still had one leaking...the remedy...the brass float had a small hole in it.  Take that float off and shake it.  If you hear fluid in there that is your problem.  Do you have the original 4 cable carbs there?  Did you do a bench sync before you put it back together?  Really makes a difference.  There is a lot of info in the FAQ area on carbs giving instructions on how to bench sync.  Let us know how it goes.  Give us a few more pics when you can...we like pics on this board.

[peten]

also check the overflow tube itself for a crack: fill the float bowl with fuel while holding it and see if it still leaks.  if it do-- there's the problem.

[Magpie]

I had a cracked overflow tube when mine did that, fixed it with a smear of JB Weld. You can also test by putting your finger over one end and try to blow through the other.
Cliff.

[cb750tom]

Thanks, for all the great info!  I think I got it.  All the seals were in good condition and the I just adjusted the float level and has seemed to take care of the problem.