I have a yz125 and the throttle won't turn. I

Two things will freeze a throttle >> a rusted cable and a stuck slide. The usual problem is a stuck slide. Disconnect the air cleaner and unbolt the carb. Pull it to one side and immerse it and the cable end in a small coffee can filled half full of denatured alcohol. Let it soak for 15 minutes. Now set the can aside. File down the end of an old toothbrush and put the new chisel end into the inlet side of the carb and under the bottom edge of the slide. Tap the end of the brush with a plastic hammer to pry the slide upward and break the slide free. The carb is going to need a through cleaning so remove the float bowl, air and throttle screws and slide assembly and let the parts soak in the alcohol along with the carb body. An hour soaking should be good. Now clean with spray carb cleaner, concentrating on the screw adjuster holes and drill circuits in the body of the carb. After reassembly, LIGHTLY seat the air and throttle screws then open up one half turns outward.

Drain the gas tank and clean it out. remove the petcock and clean it also. Install an inline fuel filter. Please rate my answer. Thanks!