is there a way to zap the brushless motor rotors

YES... Heard it is already being done

Great :( cant we just leave em alone?

some guys say yes...others say it won't work.

I heard it works kind of like an enema!

is there a way to zap the brushless motor rotors

Yes, that's how they got magnetized in the first place.

Is the equipment to truly do it very expensive along with the fixturing, also a yes.

Can you do it with a coil type zapper like was used on brushed cans, no.

Would there be any point to doing it? NO!

A magnet is like a glass and the magnetism is like water. There's no way of getting a glass of water extra full. Full is full. Guys who play around with this will claim they get the rotor stronger, but it only lasts until the magnet is actually run. As soon as you run it you're right back to where you started. Think of your really full glass of water. As soon as you try to pick it up and move it some spills out, the rotor is the same way as soon as it is run you lose a little. Then it will stay consistent at that level until you get it hotter or expose it to a stronger field.

If the magnet is like the glass and the magnetism water, why are some rotors stronger than others?

You have mentioned manufacturing variations, but what is the variation when the parts are all the same size and same material (i.e, same size glass)? Or is there variation in the material from one magnet to another? Aren't these things made in large lots? What causes the variation between magnets of the same lot made with the same material?

If the magnet is like the glass and the magnetism water, why are some rotors stronger than others?

You have mentioned manufacturing variations, but what is the variation when the parts are all the same size and same material (i.e, same size glass)? Or is there variation in the material from one magnet to another? Aren't these things made in large lots? What causes the variation between magnets of the same lot made with the same material?

Different sized glasses.

The material composition varies a lot from lot to lot and within a lot. The acceptable standard is +/-5% for the magnetic properties of the material. That along with dimensional tolerances and maybe how they are sintered (don't know on that point) stacks up to having a fair amount of variation.

From what I've learned on the subject of both the magnets and zapping it's not all that cut and dried.

Zapping a rotor is going to be expensive and must be designed properly. We're talking about a capacitive discharge magnetizer that is about 200 volts and surges to 2-3 thousand amps. If it's not set-up properly the caps can explode (dangerous and expensive)

pmsimkins is correct about the full glass analogy. There is and probably always will be some variationin the maximum that each rotor can hold for all of the reasons stated and then some. The only time that rezapping is needed or even useful is if the rotor has been heat cycled (or overheated once) killing the magnet. At this point you could zap the rotor and get it back to where it was.

For what it's worth, in industrial magnets, they sometimes normalize magnets to get the same values. They use an oversized magnet and demagnetize all of them to the same value (within the required tolerance). This would increase the cost greatly for us in RC.

I can tell you that after the rotor is zapped on an industrial sized magnetizer it will read extremely high until it's put next to other rotors or ran a few times. Back to the glass analogy, you can overfill it a little with water but it's not going to stay overfilled if you move it much. It's surface tension with water but with a magnet, there are always some weaker parts of the material that just plain won't magnetize permanently.

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..... I would like to hear what you have to say about this