The Duzmo.

Duzmo Based Biggs 1922 Special, using a modified 1921 engine.

"Duzmo Motorcycles were started in late 1919 by the partnership of John Wallace, chief designer and the Portable Tool & Engineering Company of Enfield Highway. Most of their engines were built under contract by the Advance Motor Manufacturing Company of Northampton.

Wallace & Biggs at Brooklands on 6th May 1922

At the latter part of 1918 Wallace began to design a high performance motorcycle engine. He advertised his design in ‘The Aeroplane’ to any firm wishing to diversify after their war contracts had ended. Such a company was the Portable Tool & Engineering Company of Enfield, who were impressed enough to take on Wallace as Chief Designer. The initial plan was to sell engines to other motorcycle manufacturers. By September 1919 the first engine was ready for trials, it was 88.9mm x 76.2 giving a capacity of 475cc."

Via: Oakington Plane