Factory is 15/40 sprockets 525 chain. I went with a RK Sprocket quick accell kit with 14/40 sprocket 520 conversion. It is on Denniskirk.com at about $145. This setup, you can order by yr/make/model, cut off .3 seconds in a 1/4 mile (@11.7 sec from 12.0) and lets the bike come up alot easier to a wheelie. Changing sprocket size also changes you speedometer at +10 mph at 50 and +20 mph at 120