Many Whizzer motorized bicycles used a two-speed automatic transmission, though some early models had no conventional transmission. These early models instead used a direct belt drive from the Whizzer engine to the rear wheel of the bicycle with only one gear.
The Whizzer engines were a series of small combustion engines designed to convert any suitable-standard bicycle into a low-powered motorcycle. However, many pre-built models were available after the end of World War II. One of the most notable pre-built models was the Sportsman 300S, a model that featured both a two-speed automatic transmission and a motorcycle-style kickstarter instead of bicycle pedals.