I answered this in another thread, started by reverb.
"The rotor centre separating is a known problem...doesn't always happen, some will never see it. I replaced the spacer between the drive sprocket and the rotor with a tophat designed spacer that actually firms up against the rotor alloy as it is torqued and sandwiched between the drive cog and the rotor steel centre. If you try going down this path, you will need to dry assemble and very accurately measure the distance in both firm and torqued positions. You only want an interference fit.
The thought is [after talking to my peers] that the reason the rotor separates is from the sudden changes in speed - with no cushioning - in the motor, this change in interia is only transmitted to the rotor by the rotor's steel centre, thus the alloy is trying to whip around the steel centre as it plays catch up. The tophat spacer is meant to help by ensuring that that the rotor centre and the alloy outer both move/feel the the velocity changes as a unit.
Now, I could say that my modification is working beautifully, OR my rotor could be a good one and the 'weld' was destined to remain secure for all time [and so I provided a solution to a problem that didn't exist... for my bike]. But I can't argue with the fact that its working. Sorry, no idea of the actual mileage I've done with it, but it would be [guessing] over 10,000, and very likely 3 times that?
I also increased the thickness of the spacer [as well as the width obviously, otherwise it wouldn't match up with the rotor] to centre the rotor in the stator, mine was recessed and to my mind this doesn't seem to be the optimal position. Can't remember by how much sorry, but probably around or less than 1/4"???"
One day - if I ever take it apart - I will take measurements and photo's.
Last edited by tridentt150v; 11/13/18 5:08 am.