You know, that's exactly how it worked for me--at least for this particular project. I had the same idea some time ago--I'm guessing I was about 12 years old, but that's just a guess. Anyway, I tried using one motor as a motor and another as a generator, all connected to a little rechargeable battery pack (probably from an old remote-controlled car). When I tried it, though, it didn't work. I asked my older brother about it, and he was the one who first told me about perpetual motion, and that it was impossible. As much as I would like to prove it wrong, I honestly can't see it actually happening. Sorry to disappoint.
Der Strom