Its a conical joint thing: 1980 Bimota SB3 in Houston
Here is something a bit unusual, a pre-bankruptcy Bimota SB3 that looks like it was actively ridden. Bimota was founded on the idea of taking an existing bike and making it better, with particular focus on the frame. The SB3 debuted in 1979 and while not as dramatic looking as the SB2 it was derived from, the…