A couple weeks ago while scanning Craigslist I found a 1986 K100RS for sale with less than 50k actual miles listed for $450. I've been looking for a classic K bike to take on a cross country trip, so I called up the guy and without any haggling on my part he said he'd take $400 for the K. Had previous lookers not tried to kick the tires the bike probably would have been sold before I got to go see it.
After rebuilding the stuck fuel pump and lapping the parts together to restore reliable operation, I was able to get it to run. Fuel was fed from a mason jar since the tank is an absolute mess inside (but aluminium--no rust!). The white thing on the bottom of the pump is a Bunn coffee... erm... flat bottomed fuel strainer. I poached a brake caliper dust seal for an antique mini cooper from the shop to reseal the top of the pump housing. It won't last long in gasoline, but it was a free way to get a listen of the engine running. With vacuum leaks I later found on 3 of the 4 throttles, the bike idled poorly. However, with a few grand of revs in her the engine is smooth and healthy sounding. Great, time to tear it apart!
Now I have the fairing and transmission off for a spline lube and clutch inspection. Unfortunately the clutch cover was seriously stuck to the flywheel. I got the cover off by tapping and prying, but I bent the friction plate in the process. Shoulda just left it alone
I'll probably source a used clutch assembly. Even at around 40k miles the plates seem to have around half of their life left.
The K will need a few rubber bits, mirrors, turn signals, etc. but so far there is nothing alarming. Total cost so far:$400 and about 12 hours of futzing.