A word of warning. I started looking a little into motor assist bike mods a few years ago, and very quickly you find that the biggest mistake people make in this area is not altering any of the other systems of the bike. That is, they'll put in the motor, and then just ride. Which works, but then you find that your brakes aren't quite good enough to stop quickly at the new higher speeds. Shocks are no longer good enough to prevent certain issues as well. Maybe the frame needs reinforcing... I don't quite remember the whole laundry list.
I don't know how important some of these improvements are, I just remember reading this advice more than once, and safety is important. So be smart and do your research.
I don't know how important some of these improvements are, I just remember reading this advice more than once, and safety is important. So be smart and do your research.