I can pretty much assure you that you would have to license and insure it as a NeV, if not a full-fledged motorcycle. Shoot, any engine that will go 40 MPH on a "normal" bicycle would have that thing above 60 MPH, since the majority of power that's required for bicycles is just to overcome drag/wind resistance. With that thing, there's almost no drag.
Actually, the drag coefficient would be
exactly 1/10th of a bicycle, so it would only require 1/10th the power for the same speed, compared to a bicycle. If I had the money, I'd buy a full setup, then put a fairly powerful electric motor on the rear wheel.