you "suspect"? was the float full of gas the first time you opened the carb? just as likely the seat is buggered - is the needle new? if the float is actually leaking, you could try resoldering the seam, or other spot where it leaks - if you're sure you can do it right w/o adding a lot of weight
prolly the expanding spray foam used for insulating touchup in houses is what's meant, but hafta be real careful or too much will turn the float into a ball shape that won't work very well!
also, hafta reseal the float anyway as the gas would prolly disolve the foam - easier to find another float [if needed]
Bill
