cant see that here at work, but from the description, sounds a bit like me when I wrote off my mates 1979 Z1 by sticking it in a ditch. the front end stopped dead, the seat punted me up the arse and I was catapulted over the bars to land about 40 feet away on my feet having done a full somersault. I remember thinking "that was close" as I passed a large pine tree while in mid rotation.