I was looking at this engine and thinking it looked familiar. I'm no mechanic so I had to do an advanced search through the memory files for where I had seen it before and then it hit me.
It was here at the Bomber Command Museum in Nanton, Alberta and it was this engine:
Obviously the bike doesn't have this exact engine, this one is from a vintage airplane, but radial engines are associated with airplanes. So, is this a bike with an airplane engine? It would seem so. Then I found this picture alone with this website describing it in more detail.
Why? Motorcycles already fly, do they need airplane engines too?