I was able to use a pin punch and tap the ball bearing into the bearing blocks so as to get the spur gears exactly centered on each other with just slight endplay.
I think that it is more important that the head of the armature be in the correct position between the field. The spur gears have flat teeth, what does it matter if they are off center a bit?
I was thinking that you moved the motor bearings. Interesting trick. I am going to try doing this the next time I see a worm shaft with a lot of play. Worm shafts were used in the 1946 Berkshires and Turbines, as well as in the earlier F3's.
Brushes: yes, it would be great if someone made brushes to the original factory specs, or at least got them as close as possible.
The brushes I last purchased from Lionel are probably the worst, as far as resistance goes.
Over the years I have also wound up with brushes that were much too abrasive to use.
I have a box of brushes that I would never use. I don't know why I keep them.
Coil springs of all types (not just brush springs) are an issue too. Many times the springs are physically close to the dimensions of the originals, but have a different stiffness / tension. I assume this is due to them being made from a different material.
