Excelsior's Super X motorcycle could well have been a Harley-Davidson back when Arthur Constantine presented his new unit construction 45 cubic inch V-twin design to their upper management in 1924. Disappointed in their rejection, he rolled up his plans and joined the Excelsior Motor & Supply Company, the manufacturer of Excelsior and Henderson motorcycles. Ignaz Schwinn's company was much more receptive and built the new Super X engine using current Henderson chassis parts to economize the production in late 1925.