imported post
I had the same problem you are having. The PO apparently had misadjusted the carbs way out of range before me.
The following is a post I made in November 2007.
On my 1983 GL 1100A, when I removed the arm at the #4 carb (thatcomes across from the 1/3 side), itwould just slide on and off with no pressure. This indicates that the 2/4 carbs are in the closed position. We got the same results you stated about adjusting the screw one way would increase the idle and no change to #4 vacuum. With the 2/4 carbs butterflies closed, the adjustment made the arm move back toward the 1/3 side increasing idle. I may be wrong but I think we were, and you are, working in a range of adjustment that won't give the desired results without a lot of back and forth between engine idle screw and #4 adjustment screw.
With the engine off, at the#4 carbremove the cotter pin and slide the arm off. Don't lose the washers. Adjust the screw at #4 carb (I think counterclockwise) so that when the arm is placed back on the shaft the 2/4 carbs open some. If you watch the pin that the arm connects to, it should move toward you. On mine, at the pin to arm connection,the leverattached to#4 had to moveabout 1/16 inch to fit on the arm opening the 2/4 carbs butterfly. Replace arm, washers, cotter pin, start engine and check if desired adjustment can be made.