While adjusting the stock Hitachi carb on my 1987 Samurai I inadvertently turned this screw instead of the idle adjustment screw (see attached image with red arrow pointing to the adjustment screw in question). I have looked all over and cannot figure out what this screw controls and how to get it back to the correct setting. It shows up in lots of diagrams and photos but I have not found anywhere that it is identified or discussed. Does anybody know what it is, what it does, and how to set it correctly? Thanks!

I figured it out. It is the cold/fast idle adjustment screw. Should be set to ~1,500 RPM for a completely cold engine. Warm idle setting (the upper adjustment screw) is ~800 RPM at warm operating temperature.