1990 fzr 400

Hi Danny I have a 1988 fzr 400 with a similar problem, when i got the bike the engine oil was like petrol so i changed it i have managed to get it going but only with the air box off. It idles fine an revs up smoothly when you throttle it. I have been able to ride it with air box off, when i but air box back on it doesnt rev and it is unrideable but it does idle. seems like it is too rich or the floats are set wrong? also one of the EXUP cables is snapped and the valve is kept open with a piece of wire may cause bogging?. any ideas of what could be happening here would be appreciated cheers Reagan.