77 gs 750

[CodyLavigne24]

I have a 77 gs 750 number 3 cylinder doesnt fire until i hook up the vacuum line that runs from the petcock to the carburator then the bike will run only with the choke on full. The vacuum line was plugged with screws in the hose.
what do you guys think. The vacuum lines on number 1 2 and 4 are hooked up and soon as i plug in number 3 it tries too die.

[nickr234]

Well first we need some more information, what have to done to the carbs to make sure that they are clean? are you running stock airbox/exhaust? sounds like someone tried to mod that bike in a wird way. so first thing i would do is make sure everything is stock. also with these carbs there is only one vacuum line which runs from the #3 carb to the petcock. there are line on the bottom of the carbs which are for the over flow, and then there are two vent line that should be on the top were the 1+2 and 3+4 carbs connect to eachother. the vent tube for the 1+2 and 3+4 carbs should not be hooked up to aything, you can plug them up or just leave them be. if you plug them up they might make the bike run a LITTLE richer but not much. hope some of this help, get back to us so we can help you out more.