Where do Vacuum ports go?

[Guest]

I have a 79 GS750E and I got the carbs rebuilt this weekend. They're back on the bike while I paint the tank, but I'm having a hard time figuring out the vacuum ports. I know one goes to the petcock. But there's 2 more on my carbs! The fuel level gauge has a vacuum port on it, so I'm figuring one goes there, but I can't for the life of me figure out the third! I have a Clymer manual, but it doesn't include any vacuum diagrams or other information.

I've attached a picture of the carbs. You can see the 3 ports with caps on them for tuning. Any help is appreciated.

[Big T]

The middle one is the vacuum port
The two outside ones are vents and should be open, with hoses over the airbox
The one on the fuel sending unit is a drain and does not connect to anything

[Redman]

I dont know VM carbs......

But I can say the hose on the gas guage sender unit is a drain line.

[Steve]

Agree with all of the above.

The port on carb #3 is the only "vacuum" port.

The ports on carbs 2 and 4 are VENTS, their hoses should drape back, over the airbox. If you look on the back of the right side of the airbox, you might see a rectangular loop. Your vent hoses should go through it and end just below it.

The port on what you are calling the fuel level gauge is really just a safety drain around the fuel level sender. Just in case the sending unit leaks, the safety drain will catch it and send it through the hose, past the hot engine, down to the area below the swingarm pivot.

.

[WMurphy]

Thanks so much everyone! When I got the bike, the air screws were all shut down completely and it dumped unburned fuel out the exhaust. I got it running a lot better, but only just got the carbs done now that the snow has come.