Problem Adjusting Carbs on 912ULS

After overhauling the Bing 64 carburetors and during the carburetor sync., I was unable to get the idle on one carb below 2150 rpm. I was wondering if the Idle jet adjustment screw on the bottom of the carburetor could solve the problem. This is the one that is usually adjusted by screwing it all the way in and then unscrewing it one and one half turns. The one that "rarely needs adjusting".

Any ideas would be helpful.

Ernie