IF you are refering to the little screw on top of the carb that has a spring in it then no you are turning the wrong screw. Thats the throttle stop screw. The high end needle valve adjustment screw is the one on the back of the engine. If you were behind the plane and looking at the engine from there on the left hand side hanging out is a small hand adjustable screw and when you turn it, it clicks. Turning it out will richen and turning it in will lean it out. Make sure you follow the mfg recomendations for running the engine in on the ground. THe reason for doing so is not for just getting the motor started but for breaking in the engine. I am not sure if its a ringed engine or an ABC engine. I believe its ringed and the process of starting it on the ground at the settings they tell you is to seat the ring properly and so all of the parts meet the right way. Hope this helps