Perhaps no other single development has given so much impetus to the single-hand held power tool field as has the lightweight, compact, gasoline-powered engine. This paper describes the many innovations required to develop the three models of the Ohlsson & Rice Compact engine. This versatile power package, weighing less than 4 lb, has opened up new markets for the imaginative tool and equipment design engineer. To date it has been adapted to such widely diversified equipment as motor bikes, cultivators, saws, generators, and similar units. Even wider application is inevitable because of its ruggedness, portability, and easy starting.