Engine: air-cooled, four-stroke opposed twin
Displacement: 36 cu. in.
Bore x Stroke: 2.75 in. x 3 in.
Carburetion: single Schebler
Here’s a interesting motorcycle trivia question: Which of the following companies was first to build a horizontally opposed twin-cylinder bike—BMW, Indian or Harley-Davidson?
BMW is famous for its opposed, “boxer” engines, with the cylinders sticking out the sides. The company has been making bikes with that engine configuration since 1924, which is a long time.
If you’re a knowledgeable motorcyclist, you know that during World War II, Harley built a clone of a BMW military bike with a boxer engine. But that was a couple of decades after BMW’s first boxer.
So that makes BMW first, right?
No, because before the first BMW hit the road, U.S. manufacturers experimented with the opposed-twin design, with the cylinders oriented fore and aft in the frame.
First, Indian built the Model O, a 15.7-cubic-inch (about 250cc) that lasted only three years. And then, in 1919, Harley began building this obscure machine, known as the Sport Twin.
The Sport Twin, introduced just as World War I was coming to an end, was a radical departure for Harley-Davidson. Then, as now, Harley was known mainly for its big V-twin machines.
But as Ford’s Model T drove down the price of automobiles, U.S. customers found themselves facing higher prices for two-wheeled transportation than for four-wheelers. So the move was on to build smaller, more efficient bikes.
Bob McClean, former president of the Antique Motorcycle Club of America and then owner of this rare 1922 Sport Twin, noted that it was clearly influenced by machines produced by Britain’s Douglas brand, which pioneered the opposed-twin design more than a decade earlier.
In building the Sport Twin, Harley took Douglas’ lead in orienting the cylinders in line with the frame. The side-valve engine displaced 36 cubic inches (about 600cc), and McClean said the Sport Twin made a nice middleweight motorcycle.
“The big old Harleys thumped and bumped,” he noted. “This was more of a gentleman’s bike.”
That made it a big seller overseas. But in the U.S., it was a different story. The machine languished in the Harley line through 1923, then was dropped.
Yes, it made for low-cost transportation. But increasingly, Americans were looking to Ford for that. Those who bought motorcycles wanted performance—just what they could get in Harley’s big V-twins.