Born December 1939. Began road racing in Canada in 1955 and in 1960 raced in the Isle of Man TT (DNF). From the following year, focused on World GP competition (350cc, 500cc), and in 1963 was ranked 6th in the 500cc class on a Matchless. In recognition for his achievements, in 1964 Duff was signed on to the Yamaha Factory Team. In the Belgian GP, became the first Canadian to record a victory (250cc). From then until 1966, remained with the Yamaha team, recording a total of three wins in the 125cc and 250cc classes.
The following year, 1967, raced in the Canadian World Championship Motorcycle Grand Prix, held to celebrate the country's 100 anniversary. The first ever GP to be held in Duff's native Canada, this was also his final GP. He came third in the 500cc class on a Matchless. However, Duff's passion for racing did not subsequently subside and he continued racing in the Canada national championships. In 1969 he won the 250cc, 500cc and 750cc classes, and announced the end of his racing career.
|Year||Class||Result & Pole position||Machine|
|1964||250cc||4th||PP: 0||1st: 1||2nd: 1||3rd: 1||RD56|
|1965||250cc||2nd||PP: 0||1st: 1||2nd: 5||3rd: 3||RD56|
|1965||125cc||6th||PP: 0||1st: 1||2nd: 0||3rd: 1||RA97|
|1966||250cc||9th||PP: 0||1st: 0||2nd: 0||3rd: 1||RD56|
|1966||125cc||10th||PP: 0||1st: 0||2nd: 0||3rd: 0||RA97|
*Results for years with a Yamaha factory team, riding a Yamaha factory machine or ranked 5th or higher riding a Yamaha production racer (World GP, World F750)