GS750 carb positions

[jroels]

Hi Guys,

I'm rebuilding a 1978 GS750. I just finished the engine and now I'm doing the carbs.
I disassembled the carb rack to have them ultrasonic cleaned but there are a few things I need some help with.

1. I can't figure out how to identify the correct carburator positions for putting them back together.
The #1 and #4 are easy, because they have a single sided fuel connection.
But what about #2 and #3? Is there a way to identify them? Some pictures:

https://goo.gl/photos/xaQBAYvizRDnMkgJA

https://goo.gl/photos/n4ADqCk3GCW5oj7cA

2. When I took the carb rack from the bike, the vents connections between #1 and #2 and between #3 and #4 were connected with a piece of tubing, but nothing between #2 and #3. Is this the way it's supposed to be?

3. When looking at the carbs from the bottom with the bowls removed, I noticed that 1 is different than the other three.
The carb that was is position #3 has a brass plug in what I believe is a vent hole, while the other three carbs have 2 open holes.
Any ideas on what the purpose of this plug is?

Carb #1, #2 and #4 look like this:

https://goo.gl/photos/sX656pWP95BWxzA27

Carb #3 looks like this:

https://goo.gl/photos/BXdyitFFCQjUhmV29

Here's a picture of the engine so far

https://goo.gl/photos/R4wXxjrZDnVmG4UaA

[SIMONK]

I asked this question last week in this forum ..title vm 28 123 or 4 .. have a look at the replies its basically air screws go left on 1 and 2 and right on 3 and four (sat on the bike looking down) and the petrol rail main feed is blocked on the left of 1 and on the right on 4 that is enough info to sort them ...

[jroels]

I asked this question last week in this forum ..title vm 28 123 or 4 .. have a look at the replies its basically air screws go left on 1 and 2 and right on 3 and four (sat on the bike looking down) and the petrol rail main feed is blocked on the left of 1 and on the right on 4 that is enough info to sort them ...

Thanks! That sorts out question 1.
Apparently I didn't get the search query right to find your thread.

Did you notice the brass plug in carb #3 on yours?

[allojohn]

Question 2: I have no tubing between 2 & 3, so that is correct or mine is missing too.
Question 3: #1 carb has no vent, unlike the other 3. This could explain the difference.
Question 3: Brass plug - #3 provides vacuum to the petcock, the brass plug probably has a role in this.

[xl CR1ME lx]

I just disassembled my 78 GS750 to rebuild, however I took pics of them before doing anything. Should help answer 2 & 3. Hope the pics aren't to big. The two hoses with screws in them are vent hoses the previous owner plugged for whatever reason....