After the engine is fully broken in you will run about 1 1/2 on the main needle with a std muffler. I usually end up richening up the bottom end about 1/16 of a turn from the stock setting. The OS needs a rich bottom end to keep the mid range from leaning out. You should have the bottom end rich enough to notice some coughing when transitioning to running rpm's from idle when the engine is cold. If it dies a lot when trying to run it up lean it a little but not too much.