William. Make sure the air gap between the sprocket halves are equal. Try to use a thumb to hold down the sprocket half firmly on the sprocket carrier as you tighten the Center bolt. Make sure your sprocket half spans the split in the sprocket carrier and does not line up with it. Make sure your sprocket carrier is true as far as left to right runout. If not don’t throw it out have a friend with a lathe use a piece of an old 50mm axle and take a few thousandths off until true. We race the 401 also runs nice. Good luck.