Its a cheap multimeter and the common port is broken. It still works the way its plugged in, but reads the inverse. Works for stuff like this.

I've read about water-dipping motors to wear in the brushes to the comm. But the water is only for the brushes, so I figured why dip the whole thing? Have some syringes I use for precision stuff, so I filled one with RO water, and the other with 99% Isopropanol Alcohol.

I actually compared this to a silver can that I just threw in and ran. The comm on that one is scored and nasssssty. Might try it on that one and post a before and after.

I run it on a single AA, and use Labelle 106 on the bushings. Couple drops of water on the comm and it starts to work its magic. As it starts to drag running voltage down follow with alcohol to clear the worn brush material. Repeat until the brushes are about 90% worn in, final squirt of alcohol followed by compressed air. re-lube bushings and run.

Wow. It feels smoother, maybe even more responsive I'd dare to say. Who knows, but it seems like a strong little motor.

And as for the final comment; Yes, a mess it is.

The water method is good for original silver can. The torque and sport tune have much softer brushes.. if you submerge them, they will be done for.. just a simple flash or squirt is enough to break them in

What is the largest 48p pinion that fits under cover before you have to cut it

Do you mean "spur" gear?
At the very least, the question you have posed cannot be answered without one or the other specified.....

Question. Saw the TT02 with all 419 arms. I am wondering if the Xray short arms will fit TT02. Or the stock TT02 arms handle better for rally/street run?

Yes within 30 seconds of adding the water to the brushes they wore in rather quickly, hence the alternating between water and alcohol.
Definitely a benefit to doing it but what I have read leads me to believe most who attempt it don't do it properly and get bad results.
But with it used widely in the RC scene many years ago says it did something lol.

spur is 66 48p

From what I have read, the largest 48P pinion gear you can use before it rubs on the inside of the stock gear cover is a 53T pinion.

I prefer 64P gears and my gearing is 75/51 that gives an FDR of 3.82 and post #3008 shows that I had to mod the stock gear cover to make clearance for the pinion. I later found a local guy who printed me a new cover that I have since installed.

Can I use universals in the rear of the car with the oil gear diff?

The main purpose of submerging a motor during a wet break-in is to subject the motor to significant drag, so the motor will have to work extremely hard for an extended period of time. The significant drag limits the motor's speed, which reduces the magnetic flux inside the can. The reduced magnetic flux is unable to generate as much inductive resistance in the armature coils as it normally would if the motor were spinning freely. The lower resistance allows the battery to push more amperage through the motor, and because that amperage is being pushed through a very tiny contact area between the brand-new brushes and the commutator, the contacting surfaces of the brushes get extremely hot and start to disintegrate. This accelerates the break-in process by an order of magnitude -- but it can also destroy soft brushes in a matter of seconds, as I and many other people have discovered over the years. A wet break-in is only useful (or safe) for motors with extremely hard brushes that would take an extremely long time to break-in without the continuous drag of running underwater. For brushed motors with softer brushes, a few full-throttle accelerations will put enough load on the motor to break-in the brushes, and then the commutator can be cleaned with electronics cleaner spray.

Regarding brush debris: Submerging the motor in water allows brush debris to be washed away instantly by the churning water inside the motor, whereas applying a few drops of water directly to the brushes just causes the debris to form a grinding paste that stays on the brushes. That's why the brushes broke-in so quickly for you. If it works, it works, but there's a significant risk of the brushes being damaged by so much abrasive material in such a small area.

(source for magnetic flux explanation: John Rob Holmes of Holmes Hobbies LLC)

Here's my 2nd run. Found a nice dusty parking lot. She feels quicker here than at home. Also, forgive the crash. Distracted and driving with one hand. Don't drive distracted.

Still the same setup. 23-turn motor, stock ESC, 20t pinion, 68t spur.

Picked up a TT02r kit and a complete Yeah Racing aluminum kit and built a driveway monster.
Hobbywing Max10 esc and 4000kv brushless.

Yeah Racing aluminum kit.

All is correct, However as soon as the grinding paste accumulated it was washed away with 99% Isopropanol Alcohol to prevent that from happening. I broke the brushes in in about 2 minutes. 90% of the brushes were left with a smooth finish on both the brushes and comm. And this is the smoothest most crisp brushed motor I think I have ever ran.

The one I wore in by a few full throttle runs destroyed the comm. It was toast even after cleaning it off. Chunks of brush missing and comm scored to hell.

I'm extremely familiar with motors and electronics, I used to repair Telecom Infrastructure Boards from across the US and most of the world. The company I worked for also had a DJI drone repair department.

I can swap motors out and compare the two back to back in the same TT02. Whenever I get around to it lol.

Where can I buy this part set? I want to replace the arms with Type S or SR kind. Or where can I find a Type S kit with reasonable price?