Extending the flat on N20 motors

Your motor should look like this: N20 shaft, all flat.

If your motor looks like this, you're in the right place to fix it: N20 shaft, partial flat

If your motor flat doesn't go the full length of the shaft (i.e., it looks like the red angry face picture to the right), you'll have trouble using Tyler Wheels (and other wheels). This is how to fix that!

You just need to extend that flat with a hand file or rotary tool (e.g. Dremel).

Here's a video on that: Dremel to smooth full length of the shaft