Arking coming from the motor on an Indesit 1063w Washer?

Hi,
The motor on our washing machine suddenly began to spin erratically, by this i mean it kept speeding up and slowing down shortly after this electrical arking/sparks began to appear from under the machine. After i had taken the motor out i inspected the brushes which looked to be quite badly worn, so i replaced these with new ones. Initially the motor seemed okay for a few minutes, and then it started arking again and began to get quite hot, however, the motor speed remained resonably constant. Would it be normal for the new brushes to cause arking until they have bedded in, or is there likely to be something more seriously wrong with the motor?

Thank You