Best method to clean the motor is to take it apart, clean the commutator and brushes with an erasor, clean out all carbon build up and dirt inside, relubricate the bearings, and shim the axle.

It works really good. The main reason for water is that it will take the crap away (with the armature spinning, the motor acts as a pump). And it keeps everything cold and lubricated, so a smoother finish is achieved (wet-sanding a fresh paint job anyone?).
The water needs to be conductive a little for the cleaning to work (it will help the motor turn properly if there is carbon buildup on the com).

You need a glass container (empty jam container works great).
99% isopropyl alcohol
Brake cleaner can
Duster (with the trigger)
Ultra light silicon oil (AI GBBR oil or high grade RC bearing oil. I use Trinity Royal Oil)
A rag to take out excess water

And TAP water (does not work great in distilled water... tried it).

Put longer wires/clips on the motor and put it in the container. Ideally, you want the glass to be twice the length of the motor.
Pour water up to 3/4 (about 1" over the motor).
Add a little alcohol (maybe 1/2oz.).
Run the motor IN REVERSE on 3.0v for about 2 minutes.
The change polarity and run FORWARD for 3 minutes.

Take the motor out of the water.
Fully soak the motor with brake cleaner (to replace water).
Then spray with duster to remove the excess brake cleaner solution.
Oil both bearings with silicon oil. Place a few drops on the bearing, then turn the motor by hand to let it seep in the bearing.
You will need to re-lube the bearings once in a while (maybe once a year) since it is oil and not grease.

Alternatively, you can buy a com cleaner from Parma (made for 1/24 slot cars) and replacement brushes (again, for 1/24 slots). Take the hardest "speed" brushes you can find (as you want longevity over torque... theses are made to be replaced every week).

hurrr. interesting... all the videos I saw were distilled water... not that I'd do this myself... seems to be rather involved and closer to half the cost of a new motor... and you're adding to the maintenance cycle by essentially removing all the factory grease from the bearings.

Not really actually... since no one does the maintenance to theses motors.

Once a year is the bare minimum someone should strip down his AEG and clean/lube. Oiling the bearings do not involve taking the motor apart anyways... And factory grease is far from the best... we are talking about cheap chinese bearings, not CNC and reforged ABEC7 bearings

alcohol is the one to use, h2o will leave mineral deposits where ever it dries

unless its distilled

Hm, can't wait to try this on the old VFC motor I have. I want to see how dirty that thing is.

Ever caused sparks in a glass of 99% alcohol?

Also, re-read, there is no water left in the motor when done properly. Also mineral deposit don't mater unless it's on the com... and that is exposed enough to be cleaned by the brake cleaner solution.

I guess you are not touching your motor or wires in fear of oxidation or are not playing outside because there might be dust that gets into the mechbox...

Nothing personal, but theses are toys... no need to have white-room purity products to clean it.
Also distilled water is far more oxidizing that tap water...

So I just tried this with distilled water and at first it seemed to work with a small 9v battery, then I stepped things up with my 7.4 lipo and my motor began shredding the brushes down to nothing.

This was with a 5+ year old VFC motor which I am replacing anyway.

I'll have a video up by tomorrow, hopefully. I have a hypothesis of what happened but maybe others have more experience with this.

Your com was worn down a lot, and since the water removed the dust from the brushes while turning, it literally grinded them to nothing.

Running the motor on anything over 3V was not a good idea from the start...

Yeah, the other thing that looks strange is it looks like the copper around the commutator separated a bit and caused more grinding? I couldn't get my motor open to look but does this makes sense? It continued to grind and spark out of the water. I'm a pretty big noob when it comes to motors so I hope I explained this well enough.

Yes, running the small 9v battery seemed to do little harm. In the video linked, the guy uses and 7.4 lipo so I though I'd give it a try.

Once I make this video, you may be able to see what I'm talking about in terms of the commutator separating.

It means the com is too thin (worn) and overheats. The insulation core under it melted and let the com lift from it.

It means your motor is way beyond cleaning, it's time for a new one.

Yeahhhhh, I was pretty much going to buy a new one anyway... The damn thing doesn't stick to the fridge in the slightest. Anyway, I'll still post the video for reference.

I finally got around to editing and posting this for reference.
Most of what Kos-Mos addressed is shown in the video.
http://youtu.be/SNcQBQH9yPo

Nice dance moves. Hehe.