Carb vacuum hoses

[C.V.]

1979 GS850 VM carbs, just rebuilt.

Heres the question,
There are 3 vacuum fittings on the carb rack, carbs 2,3 and 4. petcock draws from 3... 2 and 4 vent to atmosphere, correct?

During dissasembly I noticed the PO had 2 and 4 connected jumped together, as opposed to atmosphere. I reassembled the way i thought was correct (to atmosphere) but cyl 4 was not firing, (good spark, float bowl had gas, plug dry). I jumped 2 and 4 back together, and voila, I have all for cyls again.

Was I wrong about 2 and 4 venting to air, or is something else up?

[Newbee]

Vent or Vacuum?

Vacuum connections are never vented to air? Lean running, rough idle,missing among others are the side effects.

Vents are exposed to atmosphere for "venting" purposes.

I don't know about your specific setup but if you have a vacuum operated petcock then it needs to be connected to a vacuum source such as your carb vacuum nipple.

If you have any other vacuum sources they should be plugged because it will not run right if you don't.

[hampshirehog]

Your set up is spot on - 3 to the vaccuum side of the tap and 2 & 4 vented to the open air - usually tucked over the top of the airbox (on the sides).

[C.V.]

Your set up is spot on - 3 to the vaccuum side of the tap and 2 & 4 vented to the open air - usually tucked over the top of the airbox (on the sides).

Thats what I thought, untill I got no gas to cyl 4. I crossed the vent over from 2 to 4 (as I found it when i dissasembled it) and suddenly #4 was getting gas. I won't complain too much, because it works now, but I am curious as to why #4 doesn't get gas when both 2 and 4 are vented to air.

[SqDancerLynn1]

Carb 4 is still pluged, the pressure from connecting the two together forces fuel into the carb. Some remove the hose altogether when
using jet kit

[Newbee]

Hmmmm......

I guess I didn't understand the question?