I Have 1977 dt400, carburator needle valve clip position is in the middle slot, and it surges at slow speeds, if i move it up one notch, then it will not surge as much and then begins to break up at igh rpm,s and if I move it down one notch, the throttle runs away from you at an idle, got complete other carb, and switched it and it does the same thing.If I go to far down on the setting it gets worst, and to high on the setting it gets worst the other way, please help.