The Harley Sportster is considered by many to be America's first Musclebike. Light and fast the Sportster was America's answer to the narrow and lithe British sportbikes of the time. Available now as Sportster 1200 and Sportster 883 rubber mounted models, the Harley Sporster was launched in 1957 as the replacement for Harley K flathead motorcycle. The 1957 Harley Sportster featured a solid mount 55 cubic inch Ironhead engine.