The electricity passing from the motor brushes to the comm can exceed several hundred amps under heavy load. The resulting arcing, or sparking, will blacken the comm and reduce conductivity, which decreases the overall power available to the motor. A regular comm cleaning, every couple of runs, is a low-cost way to keep your motors running well between comm turnings. In electric R/C vehicles, efficiency is everything.

Simple Motor Cleaning and Maintenance

To clean your motor, get a comm cleaning brush and a can of electric motor cleaner, available from any auto supply store. This type of cleaner is much less expensive than hobby store varieties an there are even non-flammable varieties available.

The comm cleaning brush is a brush of fiberglas fibers lightly laquered together. Before beginning, wrap a small piece of scotch tape around the brush, about 1/8" from the end. This will make the brush last a lot longer; as the tip begins to wear, simply trim off the worn ends with scissors, remove the tape and put a new piece 1/8" from the newly-trimmed end.

Another method is to use a small section of electrical heat shrink tubing around the brush as shown at the left, and just slide it upward as the brush begins to wear and you trim off the ends.

1. Remove the motor from the vehicle and remove the springs. Gently slide the brushes out of the brush hoods (you do not have to remove them.)
2. If it's not already on the motor, put any pinion on the motor shaft. This will make the cleaning a lot easier.
3. Insert the comm brush into one of the brush hoods so that it rests against the commutator. While applying light pressure on the end of the brush, pinch the pinion between your fingers and give it several brisk twists, spinning the commutator against the brush. Repeat this until the commutator looks bright and shiny.
4. The electric motor cleaner comes with a fine tube taped to the side of the can. Insert this tube in the spray tip. Point the tube away from you as you insert it in the spray tip.
5. Take the motor, brush, and electric motor cleaner outside near a trash receptacle or other safe place to drip. Do not clean your motor indoors.
6. Hold the motor over the trash can by with the pinion end up.
7. Insert the other end of the spray tube into the cooling vents and motor mount holes of the motor. Begin spraying liberally, and be sure to spray in all the vents, side and top. The liquid coming out will be black with dirt and motor brush carbon; keep spraying until the liquid runs clear. The idea is to completely rinse out the inside of the motor. Additionally, the comm brush will have shed fiberglas fibers inside the motor, so it is very important to be liberal with the cleaning. This is what makes the less expensive electric motor cleaner the fluid of choice; you won't feel like you have to skimp on cleaning. Finish up with a final spray of the commutator through the brush hoods.
8. When done, blow the fluid out with an air compressor. If one is not available, this is ok; electric motor cleaner is designed to evaporate without leaving deposits behind. If this is the case, just spin the motor a few times and let it sit for 10 minutes before the next step.
9. Drop a dot of Marvel Mystery Oil or some other lightweight quality oil on each bushing/bearing, giving the motor a few spins to work the oil into the bearing/bushing. Some racers prefer to run the motor at a low RPM to work the oil inm but it's not critical.
10. Before putting the brushes back in, compare them against a new set for length and wear. The brushes shown here are slightly blued from heat and possible overheating due to overgearing. If just bashing around, this is fine, use them; racing, replace them.
11. Reinstall the brushes and springs, and you're good to go.

Before installing the brushes, compare them against a new set; replace them as required.