I purchased a 1985 K100RT with 77k miles (early model) about six weeks ago as a donor bike for a custom build. I believe I am the 5th owner. Bought it from a guy who had gotten it running and flipped it. It had been dropped on the right side so the fairings rattled pretty badly as I rode it home.
I've spent many hours browsing forums and build threads, Pinterest and Bikeexif, and have begun the teardown on the bike (actually just about ready to drop the engine and remove the frame). I'll be selling all the stock parts that are in decent condition to help recoup some of the cost of the build.
Sounds like there are a number of Austin area owners on this board!
I have started a build thread over on k100-forum.com - though right now most of my updates are going to my Facebook friends. I may start a build thread here as well.
