April 11th, 2019 
Marshall Wilson 
Harley Davidson, from its earliest beginnings, has never been a company to go with the accepted norms. They have experimented with single cylinder, V-twins (air cooled and, more recently, liquid-cooled), and opposed-cylinder engines. While most of the engines were (and are) of the 4-stroke variety, Harley did produce some small, single-cylinder 2-stroke powered motorcycles in the 1970’s when the AMF Corporation owned the company.
There were also some specialized models for use by the military and the police introduced in the early 1940’s – among them the XA and the Servicar.
The Harley XA was an opposed-twin, shaft drive motorcycle designed for battlefield use during WWII. It was based on BMW’s motorcycle designs in use by the German Armed Forces at the time. Only 1000 were ordered for evaluation, but by the time they went into production, the US Armed Forces had already decided on the Jeep as the general purpose vehicle of choice.
1942 Harley Davidson XA
With a production run from 1932 to 1973, the HD Servicar was Harley’s first production trike. It could be ordered with or without a built-in tow-bar and a small or large box. It had a rigid, differential-driven rear axle and a reverse gear. It was offered first during the great depression era in an effort to boost Harley’s sales into new markets. It became a popular means of transportation for police departments across the country.
1949 Harley Davidson Police Servicar
In the 1950’s and into the late 1960’s, Harley produced a series of single-cylinder 2-stroke bikes modeled after European models in vogue at the time. The “Hummer” is one such example. It was based on a German DKW design: the DKW RT125. This design was part of German WWII reparations, and the design was given to the three major allies, USA, Great Britain and Russia, each of whom made their own copies of the design. The Hummer was the US’s copy.
1959 Harley Hummer Model S-125
