Brushed 480 electric rc motor with bad brushes?

I have a brushed 480 electric motor from an rc airplane (hobbyzone supercub) and i believe the brushes have gone bad. The engine will idle out, and go up quite a ways in power, but when it reaches around peak efficiency it shoots sparks from around the coil inside and makes a screeching noise and the rpm doesnt even go really high. My actual question is does this sound like bad brushes or is it something else?

Shoots sparks, yes at the very least the brushes are bad. Probably what's happening is the brushes are so short the wires attached to the end of the brush are shorting out against the casing. A bad motor is a good way to blow the ESC (electronic speed control.)

The screeching noise can be the comm bushings or the comm itself hitting the magnets.

The brushes can be replaced, but I'd just replace the motor. Get one with bearings, more expensive but will last a lot longer. Try Tower hobbies:

http://www.towerhobbies.com