RE: Wattage Super Impress w/Cobalt 400 motor
To add to the Doc's advice, you want the brushes to conform to the commutator for maximum contact area. That is, they have a nice concave curved shape. New brushes are flat on the end. Run the motor a while, like 15 minutes, then carefully slide one of the brushes out and inspect it. Keep checking the brushes from time to time. When they're mostly rounded out, you can go flying.
If those 1600mAh NiMH are AA cells from WalMart, save 'em for your digital camera. They are no good for electric airplanes. Use the KAN cells.