Those caps are on there to keep home mechanics from adjusting the carburetor, which will ruin the settings for emissions control! They can be removed, but, if you take it in for repairs that you can't handle, the shop will charge you for re-installing the caps, so i was informed. I think they might have hidden slots under the caps, maybe-maybe not! And, they might have a special tool for that, but i don't know about that.
Rustyj

the newer carb adjusting screws take a special tool to adjust the mixture needles...this tool is only avaialble to service centers

I just use red electrical butt connecters, which fit on
snugly and can adjust it that way.

Fish