fuel leak

I have a gsxr 600 that has been giving me problems. It seems to be leaking fuel from the carbs into the breather hoses. the carbs have been rebuilt, twice! thinking the first guy didn't know what he was doing and turned out that I did know what I was doing. Got them back for the second time and still the same problem. some how it's still leaking. I don't think that any of the floats are sticking and nothing is blocking the injectors or anything like that. Please help me. Haven't rode for 2 years now becuase of this.[/size][/size]