I noticed a leak of final drive fluid that spins around the wheel and leaves a bit of a mess. It gets on the sidewalls of the back tire as well. I was told that the seal on these bikes are famous for going out. Any experience like this, and if so, what can I expect to pay to have it fixed? Or is there something a novice mechanic can do to stop the leak? I have ruled out the overflow tube as the source of the leak.