10-9 is for the ten tooth driver and is used to calibrate the speedo.
9-9 is 9 tooth driver 8-9 is 8 tooth driver. You change this if you change your driver size and want your speedo to read correctly.
A forum community dedicated to Ski-doo snowmobile owners and enthusiasts. Come join the discussion about trails, racing, performance, modifications, classifieds, troubleshooting, maintenance, and more!