All the little screw at the back of yur carb is is your air screw. It meters the amount of air that goes to your pilot jet. If you have to have it more than two turns out from seated then you need a smaller pilot jet; if you have to have it is less than one turn out from seated then you need a bigger pilot jet.
If you just started riding and your bike is completely stock, you are probably putting around and that is why your bike is fouling and not a jetting issue. But if you have an aftermarket pipe or porting then its a different story.