Topic: 78' 550 carb gas leak

[kuksta]

Hi everybody!

I have been working to restore a 78 cb550.  I recently got it to run and idle very smoothly, however the carb bowls were leaking a Lot of gasoline, from the overflow tubes as well as the bowls themselves.  I replaced the old bowl gaskets with new O-rings and applied some marine grease to help them stick.

Unfortunately this did not fix the gas leak problem. 

Only after I adjusted the floats did the leaking mostly stop, however the engine died after a turn of the throttle. (probably due to a lack of available fuel after i adjusted the floats)

I have been told that fuel leakage could be caused by corroded jet needles, is there any truth to this?

Any ideas or helpful hints would be greatly appreciated.
Thanks!

[unitedguitar]

I had one of the carbs on my CB750 overflow quite badly like this. I couldn't figure it out so I asked a friend if he had any ideas and he took it apart and found something lodged in the jet causing an imbalance where more fuel was being poured into the carb than was being used. Naturally it had to go somewhere and out of the bowls it came. He said if it happened again to get a small hammer and lightly tap on it to dislodge whatever is in it. Obviously this is only a temporary solution but will at least help for the time being.

[SanDogDewey]

If the float needle and seat are not clean, the float will not shut off fuel to the bowl. If your float doesn't float any more, it won't shut off the fuel to the bowl. If you float is not set right, it won't shut off fuel to the bowl or it may not let enough fuel into the bowl. If the overflow tube is cracked you will get a continual leak.

Remove your float and hold it under water to make sure it doesn't have a hole in it. Clean the needle and seat. I use a set of paint gun cleaning brushes that you can get from Harbor Freight for 99 cents. If your overflow tube is cracked, it will need to be replaced. This is the least likely problem.

[kuksta]

wow i did not even consider the possibility of the overflow tube being cracked, thank you! I will have to test them.

I have tested the float needles and they seem good

I have tested the floats but not submerged them completely, i'll try that too!