after taking the rear cover off, i pulled the rotor out and found a few things:
1) it is a real tight fit between the rotor and windings
2) it was real dirty in there (full of actual dirt/sand)
3) it looks like the dirt/sand had scratched the surface of the rotor and windings

maybe the friction of the dirt/sand was making things hot?
i cleaned it out real well, lubed up the bearings (which were fine) and put her back together. only this time i covered up the two unused mounting holes with foil tape and slipped some fuel tubing over the three leads coming out of the motor to totally seal the can. i haven't ran it yet, but we'll see...