Gas flows out of the top of the carburetor?

Sticky floats are somewhat common. The easy fix is to use a rubber mallet to give the float bowl a quick hit and see if you can get the float and needle to unstick. If it still leaks then put a fuel pressure gauge on the pump, they should have about 4-7 PSI for a carburetor, If the relief in the pump sticks you can get higher pressures that can push the needle open. Next would be to get a kit and open the top of the carburetor and check the float and then the needle. It doesn't take a lot to hold a needle off the seat enough to overflow the bowl.