If you are leaning it over past where you can sit on the seat, it will always leak gas from the overflow. On rare occasions a carb will leak on no angle, and you can tap the bowl to get the floats to seat. If its stuck, there's debris in there holding it open.
I have had to set the floats more than once, or I guess that would be called, reset the floats. Somehow, they do come out of adjustment, like Doldguy said. Getting them right makes a noticeable difference in engine performance. It also helps to fix some bike's warm-up traits like plug fouling, almost flooding at start-up, or being cold-natured. For me, anyway, floats are a crucial baseline.
