Sync carbs 2 to 3 and 1 to 4 on post 1980 GS1000?

[Guest]

I'm about to sync the carbs on my 1981 GS1000G and in the clymer manual it seems to imply that for post 1980 bikes the CV carbs don't have to exactly match each other. See the pic below of the diagram they have. I have one of those 4 dial gauge carb synchronizers so I'm not sure how the info in that diagram would apply. Am I supposed to sync carb 1 & 4 to each other at a slightly higher pressure and carb 2 & 3 to each other a slightly lower pressure? Or is it more that I can have some variation and 1 should sync against 4 and 2 against 3 but the relative difference between the pairs doesn't matter. In other words, can I just sync all 4 to the same vacuum reading on the gauges like every resource I read says to do?

 

[Rijko]

can I just sync all 4 to the same vacuum reading on the gauges like every resource I read says to do?

If you have the original exhaust (which has balancing pipes), follow the manual.
The balancing pipes cause scavenging so 2 and 3 should be lower.

If you have a 4-in-1, set all 4 the same.

Valve play should be checked before syncing carbs.

 

[Guest]

This is very helpful. Do you know what the actual vacuum reading should be for 2 & 3 vs 1 & 4? The diagram doesn't have any labels on the tubes so I don't know what the difference would be between the ball being aligned vs below the mid-line. thanks!

Andrew

 

[Rijko]

Actual value is not relevant, as long as the settings are the same.
What is important, assuming you have a 4-meter set to sync, is that you check each individual meter to the same port (which one is not important)

Connect the 4 sync hoses to 1 of the sync ports one by one.
Hopefully they all show the same, but mine show a deviation of up to 0.2 BAR.
Take that into account when connecting all 4 at once.
Or, if you have 2 meters showing identical, use only those 2.