Whizzer bicycle engines are a line of bicycle engines that were produced in the United States from 1939 to 1965. They were commonly sold as kits to be assembled and attached to a consumer's bicycle thus creating a motorized bicycle. The Whizzer bicycle engine was first produced in 1939 by Breene-Taylor Engineering, a Los Angeles-based manufacturer of airplane parts. By 1942, sales of the engines had not been entirely successful, having sold only about 2500 units.
By 1943, World War II was well underway, and Whizzer Motors were forced to lobby the United States Government for the right to continue production of what was argued to be a great way for defense workers to travel to and from work. In 1948, Whizzer sold its first pre-assembled motorized bicycle, the "Pacemaker". Whizzer motorcycle engines would cease to be produced in 1965.