I just purchased a 2001 Super Sherpa with 3800 miles. I immediately had to get a new rear brake disk because the old one was worn out. Even with the new disk, the rear brake does not have the stopping power I expected it to have and I have yet to even cause the rear tire to skid under heavy braking. Does this model have a history of rear brake problems or a known weak rear brake? I have ridden many other small motorcycles years ago and I did not experience anything of this nature. Thanks for any advice.