High frequency vibes normal, avoid bikes with a knocking engine. Good engines have a slick gearbox and relative lack of smog. Rapid rear tyre (4k) and chain (6k) wear plus atrocious fuel once a little wear gets into the bores hardly makes them worth the effort. Very rare with no sightings of nice ones; lack of spares makes rats difficult but other GT engines will fit. SB200, slower (20hp, 75mph, 60mpg), commuter version, still some left on the road.