I ended up turning the end of the swingarm into a slot and machining two adapters the fit over the axle and then slide into the swingarm slot. These adapters fill all the space between the axle and the swingarm and make it a tight fit. The adapters are steel. I left a 4" plate on the adapters that is 1/8" thick so that I can bolt this to the swingarm in the future when I go to an external controller and start having a lot more torque.
I rode it today and thing were great. Then I tried to wire up a different throttle and accidently put 48V into a hall input on the controller that is supposed to be for the throttle. So, any tips on troubleshooting the MP3 internal controller would be appreciated.
