I'm pretty sure it is siintered rotors in the ribbed can and bonded in the smoth can.. I have re-made connections to the sensor, but it is a bit fiddley if this is what you need to do, but you'll need a good fine tipped ironn, preferably temp controlled to ensure you don't muck it all up. I have had a motor with similar characteristics and the sensor wire was the reason, it was obvious though as the wire was in two bits
You can see for yourself here -
http://www.teamnovak.com/products/br...spec_chart.htm