Found a '77 r100 on craigslist offered at $2500. 70k miles. I have no other details about the bike, but I get the sense that it's a rider, not a museum piece. That's really what I want, anyway. I am totally new to airheads, so any quick tips on things I absolutly must check? Impossible to answer without more info I suppose, but does the price seem to be in the ballpark?