Early ATK's were fitted with Honda XR motors, or you could buy just the frame kit from ATK to transform your XR. Honda stopped supplying motors to ATK and that's when Horst went to the Rotax motor.
So the one in the picture is an actual ATK/Honda.
As for the Sportster, the builder saw a movie with a Sportster dirtbike in it. He tracked down the builder and found the frame was a one off C&J. He contacted C&J and they had a spare prototype frame lying around so he bought it. As it was the prototype it lacked somewhat and he had to re engineer it. If you google 'Baja Harley' you will find some info on it.
The reason it looks ATKish is because I'm guessing he styled the tank off one. I'm guessing this because I purchased an ATK tank from him which I assumed was his original plan to run.
On the ATK's the forks are the same as the early LC4 KTM forks and you can source them here for around $100/150. But you could probably fit any forks, I would be more concerned about the the rear shock as the top eye runs in line with the reservoir so it doesn't foul the riders leg. Most rear linkage shocks have the reservoir offset to the top eye and will hang out the side or interfere with the airbox. Might not be an issue on a frankenbike though, but something to keep in mind.
The countershaft brake doesn't affect the frame or swingarm, some people have retrofitted back to rear disc after having issues with the countershaft brake.
I have noticed the Yanks tend to break bikes up if they're slow to sell. One of the ATK forum members had a very tidy 260LQ that he had spent a bit of money on and used it as his regular ride. The next thing I know he's parting out the bike rather than selling it whole.
Here's pictures of all the ATK models that were built when Horst owned the factory. From 94 on they where built in Utah and Frank White owned the factory.
http://www.americandirtbike.com/newpage1.htmJust out of interest they are selling new 605 Rotax motors for $4,295 plus shipping. Should give a price index for what an ATK 4 stroke is worth.
