Help with 80' GS450 Fueling problem

[gs 450 man]

Hey Guys/Gals!
I was given an 80 GS450 and need help getting it to run correctly. Initially I had a problem where the bike would start then when it was accelerated a little, fuel would start backing up into the airbox and left cylinder untill it died or I shut it down! It's all comming in through the left cylinder and the right seems to be working fine. I have pinched the vacuum tube going back to the petcock and it seems to eliminate the overfueling problem, but now the bike only runs for about 1-2 miles, then it slows down and dies (its not fun pushing it home)! I have cleaned the carbs out thouroghly, and everything seems to be in order, floats, jets, and needles. I really need help cause I need to use this bike to take my licence test! Thank you...

[lecroy]

You may want to try something other than the performance area for this question.

My guess is that your idea of clean and my idea of clear are not the same or the float level is not set correctly or the float is damaged.