Im having a problem with my 91 cbr 600, i took the gas tank off it so i could get it painted but when i put it back on the bike runs like ****! Before i took it off the bike ran awesome... It may just be that the carbs are clogged up. But my real question is, is how is the fuel set up on the f2's? The petcock has a place for the gas and it has another place for another line? There is a vacumn line that seems to come out some where near the first cylinder, but it is unplugged and i dont know where it goes... If someone could help me out with this problem it would be great!

 

The vacuum line goes from the number 1 carb to the other opening on the petcock. It is required in order to allow gas to flow from the tank.

 

Although it doesn't actually plug into the carb, woo545 has solved your problem.

The hose you saw on the #1 cylinder that is not plugged in connects to the small nipple on the petcock.

The fuel system works by vacuum, when the #1 piston is on the intake stroke the vacuum is also drawn through that hose to the petcock which opens a diaphragm to release the fuel to refill the float bowls.

Without that hose plugged in you will only get a trickle of fuel if any, and as you elegantly described the bike will "run like ****"

 

THANKS GUYS IM GOING TO GET ON IT ASAP!