The Whizzer Motorbike Co. began making motors that could be attached to standard bicycles in 1939.
Usually attached to Schwinn bicycles, these kits included a two-horsepower flathead engine and associated drive accessories that allowed speeds of more than 30 mph.
In 1948, the company developed a complete motorbike, called the Whizzer Pacemaker (see ad at right).
This photo shows the 1949 Pacemaker on display at Bob Hexter's Grandview Cycle.
This $240 bike was equipped with many of the custom add-ons available from Whizzer, including the "studded" leather passenger seat, custom headlamp, rear kickstand and a 2.5-horsepower, four-cycle engine that got 125 mpg.
The bike was started by opening the exhaust and pedaling.