Voltage determines RPM and these are rated at 72 Volts so over-revving should not be a concern for you. Just don't hook up 72 volts with no load on the motor or it may over-rev and 'SPLODE.
Depending on gearing, it could possibly see 5k rpm under load. Maybe I should ask how many rpm per volt it does?
Mike -- The Electric Motorcycle Portal http://www.electricmotorcycles.net/ Electric Motorcycle Listserv http://www.electricmotorcycles.net/listserv
