The problem of synchro of one carburetor. The idle speed of the engine increase

[cinek100]

I'll try. I tried to unscrew the glass earlier but I didn't use much force so as not to breake it. This fourth vacuum gauge from the beginning did not work at all, the pointer hung in one position. Only slightly tapped the vacu and it began to indicate something. Or maybe this small screw under the cover is for reset?Looks like it youtube.com/watch?v=IGkAeI60ToA&t=45s