The Big Single-Cylinders of Past Times

Fifty years ago the word 'big' was applied to motorcycles of 350cc or over, at a time when the big single-cylinder machine was one of the mainstays of British motorcycling and there were models to suit the commuter, tourer, sporting rider and sidecare man. The lineage of some of their engines could be traced back to the 1920s, but although staunchly supported by many riders, few singles received much in the way of development in the late 1950s and as they gradually lost market share to the more glamorous vertical twins that British factories were then producing, big singles were the first models to be dropped as British motorcycle factories went into decline in the 1960s.

In 1956 Royal Enfield licensed its singles to be built in India and some 20 years later Roger Slater, of Egli and Laverda fame, began importing the Indian-built bikes into Britain.

Even in the 1950s, makers such as Ariel, BSA, Norton, Royal Enfield, Velocatte, etc... offered over 30 road-going single-cylinder models of 350cc or more, and several also marketed separate competition versions for use in trails, scrambles and road racing.
The 500cc Velocatte MSS and the cheaper BSA B33 were typical basic touring models. They put out 23 horsepower at 5500 rpm, while their sporting brothers the Venom and Gold Star achieved nearer 35 horsepower at 6200 rpm. Road tests of the time indicated that those modest outputs were sufficient to propel the \'cooking\' models to a maximum of just over 130 km/h, while the sportster reached 180 km/h under test conditions. None had fairings and all ran with four-speeds, drum brakes, telescopic front forks, swinging arm rear suspension. Almost all had overhead valves although BSA still marketed the 600cc model M21, which was a side-valver aimed primarily at the sidecar man that offered a vibratory 15 horsepower at 4000 rpm, along with a choice of plunger or rigid rear end.

Tag: Single-Cylinder Big-Bore Engine Technology Development Exhaust-Emission BSA Norton Royal-Enfield Velocatte Ariel Laverda
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