The parts catalog refers to this item as "Stopper - idle." Can anyone explain what this part does? Mine have gotten totally loose. Maybe it's sometimes referred to by another name? Two visuals attached.

Thanks hugely in advance.

Just a way of securing your A/F knob from getting any more rich. It stops the A/F knob from dropping down any further. Most carb sets have them removed, that I have seen.

Ah, now I get it. Many thanks, Duffman.