It seems the closest size for these is an FC-280 or Fk-280 motor.
I have done a bit of hunting around and if you search eBay for FC-280 motor you will find some possible options for a around $6 a motor. I can't find any that are rated over 12000rpm at 12v so the search will continue.
You can use the Autoart 1/24 motor the Autoart website was showing them out of stock
Paul Gage has an article on it at the old site
http://homeracingworld.yuku.com/topic/2 ... 911?page=1
Not quite sure how much detail is needed for this conversion. It is simply put "swap the pinion, transfer the wiring, drop the motor cover on top of the new motor, torque the screws, connect the wires, quick test, install the body" and then go kill some Scaleauto 997's! Okay, there can certainly be more, but that is a good starting point. In the pics below you can see the chassis stripped down, the old and the new motors side by side, and the empty motor housing. I just place the motor in the bottom of the chassis and drop the cover into place. The cover holds the motor securely in place and the gear lash has been perfect on every installation so far (997, C6R, F575, 2 x BTM Cheetahs, and a GT-40). I order my motors from "AutoArt Collections" website and they are delivered from a California address, the web address is listed on this topic already.
If any of you are interested, the official size of these motors is FC-280. While a few thousand are made for slot cars, millions of them are power window and door lock motors. They can be had for $1.00 to $3.00 at auto surplus outlets. Haven't found one that works well enough as a slot car motor, however the search continues and AutoArt motors are not really that much more money.
The Autoart motor is definitely rated higher than 12k rpm
If anyone can recommend a motor that would be appreciated
cheers
David
