Most 4 strokes come from the factory with the low end sdjustment horribly rich. If you could close the needle that far, I suspect that you need to lean the low end. I would bring the needle valve back to 2 turns open and lean the low end 1/2 turn. All 4 strokes vibrate much more than 2 strokes, but when their low end is too rich, they really vibrate. If you go too far on leaning the low end, the engine will stammer when you open the throttle fast; maybe even quit. Too rich though makes a 4 stroke run awful and vibrate badly through the whole RPM range.