OK. Buy a squat motor can with bearings from TinyRC. Get 0.1 uF ceramic capacitors from RS. The timing change is documented on
www.atomicmods.com (I think. Somebody will correct me if I am wrong) Break the motor in by hooking it up to a power supply set at 3.0 volts. Have the motor outside of the car so you don't wear the gears. Run it for 1/2 hour to set the brushes.