Just in case you are wondering what the stop screw does, it has two functions on most carbs.

1) it can be set to keep the thottle barrel from closing too far and shutting down the engine. Personally, I don't like an engine that I can't kill from the TX, so I back mine out to allow the carb to close fully.

2) It holds the carb barrel in the carb. Back the screw out too far and the barrel will fall out and the engine won't run to well anymore. .

It does not affect the engine running at all

(warning, overgeneralization in there, but it's close enough. In fact, many carbs use the stop screw to also move the barrel left and right as it rotates. This is done with a spiral groove cut in the barrel that the stop screw sits in. This side-to-side movement works in conjunction with the lowspeed needle to control low and mid-range mixture settings. But since the amount of side to side movement is set by the angle of the slot, it's not adjustable, it's something the carb designer either got right or didn't, and there isn't anything to do about it now).