SBP's jack shaft kit is money well spent! Take the time to read the instructions properly and it will go together very easily. It's fantastic to be able to change gears, cruise at low revs, take off on hills and accelerate down hills! I was at my local bike shop talking about my MB and the owner was saying he saw a MB that can keep up with the traffic it was going so well. I asked him where he saw the MB, it was not far from my home turns out it was my bike, oops. I now keep a lower profile but my MB goes hard thanks to SBP's!
Check my bike out but I am going to rebuild it, I have some new ideas from looking at other bikes.