I have heard of 4. One on DRN, two on Thumpertalk, one occured on a local 520. It is not 400 specific, because basically, both motors are the same. It is also not SX, MXC, or EXC, specific. I am wavering back and forth between the '02 400SX (with improved bearings), and the '02 CRF450 (1st year model - so who knows??).