The link below is to the progress made to date on a Suzuki RM125 conversion that utilizes the factory 6 speed gear-box, powered by a Unite MY1020 1200 watt motor that will be re-wound, have a brushplate upgrade and be drilled silly to handle some heavy air cooling.
The bike currently running with an open source PicOx Ver 1.02c motor controller that can deliver 48V @ 75 Amps peak.
http://www.theworkshop.ca/energy/suzuk_e/suzuk_e.htm
All the Best!
FrankG