Excelsior Super X

The Super X had originally been envisioned as a competitor to the Indian Scout which was, at the time, powered by a thirty-seven cubic inch V-twin engine.^[3][6] Indian's initial response to the Super X came in 1927, when they enlarged the Scout engine to forty-five cubic inches. This defensive move was followed a year later with a more decisive attack, the introduction of the 101 Scout.^[6] The new Scout proved to be a formidable competitor both on the racetrack and in the marketplace.^[4][7]

In 1929, the Excelsior-Henderson concern restyled both its motorcycle offerings, the Excelsior Super X and the Henderson Four, for a more contemporary look.^[5] These "Streamline" models had tanks that hid the top tube of the frame and wide front fenders with holes for the forks to pass through.^[2]

That year, Harley-Davidson released their forty-five cubic inch motorcycles, the D and the DL.^[8]

The Super X competed with the 101 Scout, the D, and the DL, until 1931. During 1931, the Indian 101 Scout was replaced by a Scout model based on the heavier Chief frame, the sport solo DLD was added to the D and DL in the Harley-Davidson line, and the Excelsior-Henderson concern ceased production of motorcycles upon the order of its proprietor, Ignaz Schwinn.^[6][8][9]

The Super X was America's first forty-five cubic inch motorcycle, and the racing class for forty-five cubic inch motorcycles was started in the United States one year after the Super X's introduction.^[3] The forty-five cubic inch class became the premier class in dirt-track racing, in which such motorcycles as the Indian Sport Scout and Harley-Davidson WR, KR, and XR would compete.

Although the Super X came to an abrupt end, its competitors from Indian and Harley-Davidson would continue for at least a decade.^[8][10]