kx250 03 needed a extra shim put in ,1mm thick that and a pc pipe did wonders.One of the magazines had a article on it years ago plus the Kawasaki race tuning information had its as well,p/n92026-1590 it goes between the bearing and the existing spacer it help the low to midrange speed transition smooth ,it worked on the 03 I had.The spacer is fairly cheap as well.