Late in 1918 Wallace returned to his first love, and laid out an advanced high-performance motorcycle engine. When drawings were finished, he cleverly advertised his design in The Aeroplane, knowing aircraft builders would need to diversify after their war contracts had ended. One such company was the Portable Tool & Engineering Co. of Enfield, who were impressed enough to employ Wallace as Chief Designer. Their plan was to sell 'loose' engines to motorcycle manufacturers, and by September 1919 the prototype was ready for trials. Clearly, Wallace had learned a few tricks from cutting-edge aircraft technology, as his engine used Overhead-Valves and was 'oversquare' at 88.9mm bore x 76.2 stroke, giving a capacity of 475cc, using a fully-recirculating oil system with two oil pumps on the timing cover; all very advanced for 1919.
Herbert LeVack (above) had been employed during the war assembling and testing aero engines, and his services were secured by P.J. Wallace to build his new motorcycle engines. LeVack proved a valuable asset, with an uncanny ability to produce wonderful results from ill-fitting components. He built the prototype engine and got it running satisfactorily; a second engine was then fitted into a motorcycle chassis, and used by Le Vack in demonstrations to the trade & public, and in competitions. LeVack's development and riding skills produced excellent results from Wallace's design. The motorcycle was first christened the ‘Ace’, then the ‘Buzmo’, before ending up as the ‘Duzmo’ in 1920.