I was just on my way out the door to buy this:
http://boston.craigslist.org/bmw/mcy/701525702.html
for 50 bucks, but after emailing with Mopedjay I've decided not to. Mopedjay said that it looked like a Tecumseh engine on it. I called the guy back (Tom - nice enough guy) and it is in fact a Tecumseh 2-stroke (itself a rare find and probably worth 200 alone). He said the engine runs, but I have too many irons in the fire to be messing with something that's probably going to need some serious tooling.
Good score for someone with a Moby or someone with a gokart.