My XR650L stock was 15-45. I had changed the 15 to a 14 for the ride, and thought that would have been fine. But during the ride there were several times when you almost lug and stall the motor going up very steep trails with sharp switch backs.You do not want to slip the clutch on a long ride through remote areas, having a reliable bike is the name of the game. I now run the same 14 on counter shaft and went to a 48 on the rear. That is equal to a little over 10% in lower gearing. the top speed of the bike is still 75MPH plus. Also the motor does not have to work as hard resulting in running cooler,and smoother.My 2 cents worth.