Tap the sides of the bowls decently hard with the butt end of a screws driver. If your floats are stuck this will free them up.
If that don't help, pull the bowls off real quick and check that the float hight is correct.
Seeing that your i there, check that the needle and seat are not worn and letting fuel by.
Here is a good link to read, with pics and will show you how to measure your floats and check the needle seat.
http://www.allthingsmoto.com/forums/f-15/how-set-your-motorcycle-carburetor-float-level-more-commentary-13608/
Taking the bowls off and adjusting them is a 1-10 on the banshee scale. So easy a cave man can do it.
Check back with your findings man.