Hi folks,

I'm assembling a 450 size quadcopter and noticed while unit testing them that one of the motors is noisy at lower RPMs.
The motor is a DJI (clone) 2212 920kv brushless outrunner. I have 4 of them and only 1 has a scraping noise as if the stator coil is getting caught on the rotating magnets.

I tried to ignore the noise and proceed to fly it, but the quad is unstable and the ESC driving the noisy motor is heating up..

I opened the motor up thinking it could be the coil, and it was.. one of the coils was jutting out and I pushed it inside. But the noise is still audible and looks like something else is the problem.

Could it be the bearings? Any advice on how to create a setup to safely remove the bearings (they seem to pressed quite tightly)?

Photos attached. In the first photo, the loose coil is visible, and in the second some black scratches on the magnets.
After fixing the coil, the magnets don't seem to be visibly touching the coils but there is still a lot of noise audible when the motor is powered up and rotating.

Nothing out of ordinary while rotating with hand.

I had the same problem! It was the shaft of the motor for me! It was slightly bent

My motor was making a click sound, when i opened it, i saw this.The blue glue type material
It was touching the motor shell. Just rubbed it with sand paper and thats it.

Thanks, I suspected that too, but when the motor spins with the propeller nut/cap on, I cant see any wobbles so dont think its the shaft

Unfortunately as you can see from my pics, there's enough clearance between magnets and stator body.. so that's not it.

You have an impressive motor though, which one is that?

I have seen your pic, my case was different, but thought to share it .
The motor is a pancake one, 5010.

Hey folks.. sorry for the delay, but I was able to fix the noise by changing the bearings. It was from the upper bearing.

These motors use 3X8X4mm 693ZZ type bearings, which luckily I was able to salvage from a cooling brushless fan I had lying around. These are also available on ebay.

Another stroke of luck - the retainer E clips kept flying away and I didnt have a spare. I somehow managed to find them and put back the motor