blowing a greenish liquid into air box

hello i am new to bikes and just aquired a 1982 yamaha 750, this is my problem, i just rebuilt the carbs and put them on and fired the thing up for the first time, this bike has sat for around 5 yrs, it was smoking like a cheap cigar, then it started to blow a greenish looking liquid, almost like an oil, gas, water mixture into the air filter box, now the port it is blowing from has a hose that goes to the transmission i would guess just to the rear of the shift pedal, what is cauing the blow back and what could it be that is blowing out besides gas?