[suicideneil]

You can test if the rotor is ( badly ) unbalanced or not yourself- you just need some bearings and a non-magnetic stand to sit either end of the rotor on to spin it- a couple bits of wood with a V-notch for the bearing to sit in would work.

Also, consider that is the rotor was unbalanced enough to be a real problem, then the whole motor would vibrate like your mobile phone as it spins. If it just sounds a little off and isn't vibrating, and the temps are fine when you run it in a model normally, I wouldn't really worry so much- chances are it would have failed/shattered or turned into a washing machine full of bricks by now if it was a serious issue..