It's only an engine. Then again, carburetors sometimes suck!
The float has a small rod running through it with a point on one end. The pointed end fits into the float needle seat in the float bowl cover. With the cover removed and the gas line attached, you should be able to start and stop the flow of gas by lightly seating the point in the needle seat. If you can't do this, there is something wrong with the seat which should be easy enough to see with a magnifier. If this does control the flow of gas, make sure the float has no gas inside it by shaking it. If it does, replace it, if not, drop the float in the bowl with some gas and make sure it bobs around freely. If not, clean out whatever interferes with it. If it is ok, you don't really have a problem.
It's only an engine, but carburetors sometimes suck : )