It isn't necessarily the motor either; I've seen a couple units that
require some kind of "disc present" feedback from the laser diode before
they spin....lots of adjustments possible here. I'd start checking power
supplies, and putting a scope on the motor drive, might tell you if you're
barking up the right tree.
As for motors though, I've found slow speed computer CDROM drives can have
compatible motors -- if you find one that will mount properly. I got sick
of trying to find compatible parts; and so, I've been working on converting
a 101-disc cd audio changer for use with data cds and dvds.
T.H.x.
Devon