It could be that your sprocket is mis-aligned. Split sprockets are not generally two identical halves, and do need to be joined back together in the correct orientation.
The factory generally makes this process easy by providing an index mark / aligning mark on each of the halves which provide a reference for the completed sprocket.
Simply find the two reference marks (usually a line indent) - one on each half. Then orient those so that the meet each other.
- SPR005S_JOIN_500.jpg (22.65 KiB) Viewed 6561 times
You should see two small divets/lines as per the picture above. There are only 2 of these – one on each half. When the sprockets are arranged so that the line on each of the sprockets meet then you have it correctly oriented.