Regarding that pull you feel when turning the motors by hand I can feel all of the little "grabs" and if I recall correctly they are pretty pronounced on my solo. As if they were a few mm or so apart. Should we not be feeling that?
You always should feel the "pull" of the magnets, if not then it no workie.... The degree of the pull is the question. it appears that several of the CW/Black motors have a greater pull than the comparable CCW. At speed the effect diminishes....so I think it is a rabbit hole to consider it the offender. At least at this time.
FWIW, the correct term for the magnetic pull is Cogging Tourque or Detent. There is an IEEE paper on the subject. The paper basically says it is either the stator, magnets or the bell roundness. There's more than that, but for our purposes that's enough to isolate a cause.
I had written the above reply last night and then realized I had never measured the run out for the bell housing. So I set up my dial gauge, mounted the #4 motor pod off my table saw fence and proceeded to measure the run out. To my surprise the bell was running a little over .001" out towards the exposed bottom portion of the bell. The location of the difference was opposite of one of the grub screws, the one set to the flat of the shaft. The top side of the bell had very little run out if any.
So there is a possibility that the shaft alignment is the source of the excessive Cogging Torque. Allowing a set of magnets to be closer to the stator. I've never been concerned about run out before in machining, since it is a tolerance related to the machine itself. True the machine and run out should not be an issue.
I measured another CCW motor pod, which had very little Cogging Torque, and it's run out was tight. Interesting and it confirms a possible reason for the perceived issue.
My question remains, does Cogging Torque contribute to vibration while the motor is running? Obviously the run out does, but could be compensated by balancing with weight...just like they do during assemble of the motor. Take a motor apart and you see the epoxy plugs in between the magnets as balancing weight....
And yes, I removed both motor pods several times and remeasured to confirm my process was not flawed. About 6 times with the #4 CW and 3 times with the CCW. If anyone has the proper gauges, I'd appreciate any confirmation that agrees or disagrees with my findings.
This could be as simple as how the bell cap was drilled to accept the shaft. You'd presume they ran the CW on one machine and then the CCW on another....