What (besides heat) can demagnetize a motor?

[bdebde]

I have again demagnetized (or nearly so) my Plettenberg Big Maxximum. First time around was with my MGM16024, with less than 30 min. run time. I sent in for warranty repair, but they blamed the controller. This time around I only got about 15 min. on the MMM. I never ran more than 5 or 10 min at a time as I was still trying to make adjustments and had to stop and do that. Temps never had time to get very hot, 130 - 135 F, maybe 150 after the motor started acting up (after getting demagnetized).

Plettenberg said to set controller for 4 pole motor and the part number say P4 (4 pole), but when I ran it on the MGM set to 4 pole, I got a reading of 75,000 rpm. This would not be possible with a 2300kv motor on 6s. If I set the MGM to 6s, i get 50,000 rpm, which is right for 2300kv on 6s. I wonder if something may be mismatched; windings or rotor. Is it possible to have 4 pole windings and 6 pole rotor, (or vice versa), or is the poles all dependent on the rotor.

I can't help but think something is not right, and of course they (plettenberg) are going to swear up and down that all is right and good with their motor. I have only manage to demagnetize one other motor, a Nemesis blue 8XL, but that was nearly 30 min. continuous running and it was near 200 when it went, and was in a different vehicle. Then FD replaced it no problem.

I have run at least 4 different motors in the same rig on the MGM, and 2 motors with the MMM. All worked well and ran cool. I even ran a 7XL on 6s and it ran much cooler than it ever did on 4s, and it was every bit as powerful as the Big Maxx (I have to agree with Serum on that one).

I am just trying to decide if I should just by a new rotor for this thing or if I should rattle Plettenbergs cage some more or just write this (now very expensive after repair) motor off as loss. So any input on what else could have happened will give me some ammo to fire at Plettenberg. Thanks guys.