I like to photograph motorcycles with a 50mm lens. I saw this Harley-Davidson parked in downtown St. Petersburg Florida. Using a 50mm f/1.8 lens lets me select only a part of the motorcycle to show in focus by using a large aperture creating a shallow DoF. I like this style for motorcycles where the bike is shown in ever increasing blur from front to back.
Using a 50mm lens up close also means the whole motorcycle cannot be fit into the frame, which I think is a plus. It is much easier to get creative with composition with focal length restrictions.