Tried taking it apart, no dice. Had to buy a 27mm socket to get the nut off the pulley. Odd size.
22mm keyed front shaft:
14/12mm tail shaft:
Thought I'd lost the key...spent 10 minutes looking for it on the floor, only to find it hiding on my bench under the motor.
No photo, but good to note...the 4 big bolts clamping the two halfs of the unit together are in a lovely square, making it 6" square in the middle...nice and tidy for use as mounting points.
And on a side note, I had a regular alternator pulley on my bench, and it just happened to be the same 17mm that both my treadmill motors use. Nice fit:
Can probably turn it around and make it closer to the body of the motor.