Topic: CB550F carb #1 leaking from overflow

[Kent624]

I could use some help on a 1975 CB550F. I am having a fuel leaking problem. I double checked and all floats are at 22mm. Carb #1 leaks out of the overflow tube intermittently while riding. In the beginning of the ride its fine, but after about 15 minutes, it starts to leak. Sometimes it will stop leaking and others it just doesn't stop until i turn the petcock off. Yesterday when i parked it and shut off the fuel, 2 minutes later carb #1 starts leaking. Knowing my petcock drips slightly, I took the tank off thinking fuel is still getting to the carbs and thats why its still leaking. This morning i go outside and theres a pool of gas from carb #1 on the floor. How is it possible for it to leak without a tank on it? I'm going to take the carbs back off and move the float and bowl around to see if the problem moves with it. Any other ideas? Could the overflow tube in the bowl be cracked? I've rebuilt the carbs with new parts. All the parts that could be replaced, were.

[flybox1]

you can easily test the bowl overflow pipe by filling the bowl with water and leaving it in a glass for an hour. if the glass is dry, move on.
you need to ensure your tank is free from debris and your petcock sock is not damaged.  anything washing down thru the petcock will block the float valve.
if tank is clean and the overflow pipe is not cracked and leaking, you need to verify your float height, and, verify your float valve is not worn or not sealing.

do all of this off the bike with the carbs propped up level. 

if the float valve will not shut off gas you'll need to buy a new matching set (valve, and seat).  4into1.com carries these...

If your float valve shuts off gas, then verify your float height, and "test" the fuel level by using the clear tube test.

No debris, functioning float valve, and correct fuel height....will always keep your fuel in your bowl.... and the majority of the time, even if you have a leaky petcock.