Named after engine designer Sir Harry Ricardo it featured an innovative four valve head design and was capable of over 70 mph, set three world speed records[1] and won a gold medal in the 1923 International Six Day Trial.

Harry Ricardo's final design had the four valves operated by the existing tappet mechanism and set a new standard for the power output possible from a 500cc single-cylinder engine, achieving over 20 bhp – the same as a 1500cc car engine of the time.

[2] Capable of 70 mph, the four-valve head allowed more efficient gas flow and the spark plug could be positioned in the middle for optimum combustion.

This had a poor reputation for handling, however, and was not really built for the more powerful four valve engine.

[1] Triumph had a poor result when three Ricardo's competed in the 1921 Isle of Man TT, with only one completed the race but a 'Model R' Fast Roadster model was entered in the 1922 Senior TT, ridden by Ricardo's assistant and fellow engine designer Frank Halford, who came 13th.