What Doug said,

and also: while you're in there take out the floats and completely submerge them in a tin of water or fuel. Look very closely [especially if you used thicker water as compared to thinner gas] and check for any bubbles indicating leaks. On the little brass floats, not so much on plastic ones, you can sometimes shake them and listen for fuel sloshing around inside.

Leakers cause float to drop in bowl regardles of fuel height. Can be fixed with a super cleaning to bare metal and a tiny dab of JB weld. Near impossible to resolder brass ones, at least for clumsy me...