Rick,
Could there be a chance that your problem might be further upstream. If there is junk in the tank, and it makes it to the needle and seat, it can hold it open and cause the problem you describe.
I only mention this because you said it happened on the first carburetor too.
The brass float assemblies can spring leaks and sink. When you take you carburetor apart again, make sure the float isn't full of gas.
Stuart
