At the end of 1918 Wallace had designed a motorcycle engine high-performance and offered it to any company that wanted to diversify their contracts after the war ended and as a result Portable acquired the rights to produce the engine and appointed Wallace head of design.
The initial plan was to sell the engines to other motorcycle manufacturers and by September 1919 the first engine was ready for the testing. It was an attractive OHV which displaced 475cc (88.9 mm x 76.2 mm) with a removable head, aluminium piston, and external pressure lubrication using two pumps. It was a very advanced engine for the time.
Wallace was in contact with his friend and fellow test rider Bert le Vack (the Wizard of Brooklands, world record holder in the 1920s), who had gained experience during the war in the assembly and testing of aero engines.
Le Vack joined the fledgling company and built the first prototype engine which proved satisfactory during bench testing. A second engine was built and installed in a motorcycle which was used by le Vack in demonstrations to potential vendors and the general public.
The combination of skilful designing by Wallace and le Vack's considerable prowess as a test rider resulted in a great machine. Initially called the Ace, it was renamed Buzmo and finally became Duzmo in 1920, when le Vack revealed its merits to the racing world in no uncertain fashion, achieving numerous competition victories in short order. Duzmo is said to be a humorous deformation of "does more".
Success produced a torrent of large orders which the small factory found impossible to fill. In 1922 le Vack was made an offer by by J. A. Prestwich which Wallace could not match. The initial concept for the sale of engines was challenged as a result of the large of orders for replicas of the le Vack machine. The directors of Portable Tool decided to wind down production.
One of the directors suggested to Wallace that he take charge of the company, offering a loan to be repaid from future earnings. Wallace agreed and as a result John Wallace Ltd was created to produce Duzmo machines.
Initially a single-speed belt driven 500, the motorcycles developed between 1921 and 1922 had a Sturmey-Archer 3-speed gearbox with chain drive, an Amac large bore carburettor, ML magneto and Druid Mk2 forks.
In a manner not dissimilar to the creation of Irving's most famous engine, Wallace paired two singles into a 992cc V-twin for competition use, but the departure of le Vack resulted in little competition success and sales were unsatisfactory.
A new Duzmo single emerged with an unusual but quite attractive sloping tank and low seating position, running Brampton forks and a Binks carburettor but sales remained poor, resulting in the closure of the works in 1923.
The remaining stock was sold to D. J. Sheppards who attempted to market the Duzmo, but it is believed that he sold very few motorcycles.
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