I bought an old bike, a Yamaha XJ650 Maxim last year. It wasn't running when I got it, but with the manual, I figured out the electrical problem that it had. I did alot of work to it, rebuilt the front caliper, did the back brakes (there weren't any left), cleaned the carbs, got the tank sealed and I bondoed/painted it, etc.
I also put new superbike bars on it and rerouted the control cables. It's almost ready, but I have to replace the front rotor, the one on there now is warped.
The bike is kinda cool in the old way, and with the bars it handles quite nicely, much better than with the old monkey bars that were standard. I'm not sure if I'll sell it when I'm all done with it, but the project has taught me alot about wrenching on bikes and how they work. I enjoyed working on it, but not sure if I'd do it again.