Fuel in carb vent tube

[stang66clc]

1981 cb750s. The bike sat for several years before I picked it up at an estate sale. I rebuilt the carbs following a detailed tutorial. I ran it for a few miles, it ran, but not great. Now it's pouring fuel out of the overflow tubes. I have a float bowl off and am gently holding the float up, turn the fuel on, and there is no fuel coming past the float valve. After a few seconds, fuel starts coming down from within the carb. Fuel also starts coming out of the rubber carb vent cross over tube that's between the carbs. Where can fuel get into the carb vent system?

 

[93trident]

Did you use new float needle valves and seats?

 

[stang66clc]

Not new seats. Polished them with a rubbing compound though.

 

[Oscar Meyer]

1981 cb750s. The bike sat for several years before I picked it up at an estate sale. I rebuilt the carbs following a detailed tutorial. I ran it for a few miles, it ran, but not great. Now it's pouring fuel out of the overflow tubes. I have a float bowl off and am gently holding the float up, turn the fuel on, and there is no fuel coming past the float valve. After a few seconds, fuel starts coming down from within the carb. Fuel also starts coming out of the rubber carb vent cross over tube that's between the carbs. Where can fuel get into the carb vent system?

Did you use quality carb kits with all the proper o-rings? Did you test the overflow tubes that stick straight up out of the float bowls for cracks? Did you use good quality float needles?