I got a scrambler 400 2 stroke. I cant seem to get it to run right when you are puttin around the yard or where ever it runs very rich. It idles fine and if u give it 1/2 or more throttle its fine. Also the idler screw and the air mixture screw they dont do anything you can turn them and it doesnt affect anything.

 

Have you rebuilt the carb or cleaned it?

 

how is the air filter?
Maybe try driving around without the air filter see what effect that has. Unless it is dusty where you live , then don't.