You may want to check back....my bike isn't near where I can look at it, and I can't rmember!
There are 2 lines coming off the petcock. The larger hose is the fuel line, the slightly smaller one is the vacumn line. Maybe these are reversed? The larger hose, the fuel line, should connect to the front of the petcock.
There's a third line on the other side of the tank...another small one, for the gas tank indent drain.
I can't picture exaclty where the fuel line connect on the carbs. Somebody should pop in with an answer pretty quickly...