This goes along with the stuck float theory. It could have a sunken float. or a pin-hole in the float. Proabably only if you have brass floats though. It would not be stuck but would sink when in fluid. When you disassemble the bowl look to see if there is a wet spot forms anywhere on the float it could be fuel leaking out of a hole. It only takes a tiny hole also. Try checking float hieght while the engine is running to verify its corect. If it is not then replace the float.