Is this the screw for the carburetor of the mixed car 125? How to adjust it?

To be exact, this is called idle auxiliary nozzle adjusting screw, which can adjust the mixture concentration at idle speed in a certain sense, but it has nothing to do with the main fuel consumption, and this can only be used to adjust idle speed.

Generally, after cleaning the carburetor, assemble it, screw this (brass) screw to the end, and then screw it for about 1.25 to 1.5 turns to take it back. Then screw in and out with the throttle adjusting screw to find the best position.

It is very important to adjust the hole opener. If the adjustment is not good, the engine will not start easily, and there will be a transition in acceleration or high fuel consumption at idle speed.