I had a bad experiance with a York motor recently. It Had been going through rear bearings in the past and the vibration anaylsis report confirmed the need for bearings again. Assumed bearing flutting from the VFD. Pulled the motor back and installed an Insocote ceramic bearing in the rear and standard SFK 6316 C3 in the front. Seemed routine no red flags. Got it all back together and was running it uncoupled for 15 20 minites and the rear bearing literally caught on fire. Fire department, the whole deal. Well once I got over that sickening feally you get when you have #### up, I pulled it back apart and the rear bearing was in peices, the rotor had dropped enough to need extensive repair, seal cover bent, shaft scared. Had to wheal the 2 ton bugger through some terible places to get it out the door and on a truck. The bearing shows signs of fretting on the outer race and serious outer thrust on the inner race. When I listened to the bearing at start up I herd no unusal noise or excessive heat The rear bearing was warm but not hot. 10 minutes later it was on fire. I have probably done bearings on 50 York motors over the years and never had problem, but upon research of this failure I discovered a lot of things I did not know about motor bearing fits and measurements. I have always gone by how it feels in the bore and goes on the shaft, not much measuring going on, well I got burned and feel like a dumb a##. The company was good about it, I have built up a little credit over the years and now the motor is off to Ram Indutrial Service to be repaired. I was wondering if anyone has had a failure of this nature and also what type of checks do you do when installing motor bearings. I am embaressed to say but I dont even have the tools to measure a 7 inch bore to the micro meater standard as specified.The plane angle or bore straightness is measured in minutes of angle for gods sake. After a through evaluation of the bearing and motor I have come to the conclusion that I dont know what the heck happened. Thanks for allowing me to vent a little.This job can sure be humbleing. The motor is a Ram 765 HP 5010DZ Frame, 460 V 3600 RPM.