BSA Motorcycles Sloper S31-9 1931
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| Manufacturer | BSA |
|---|---|
| Production | 1927-1935 |
| Class | Standard |
| Engine | 493 cc (30.1 cu in) OHV |
| Top speed | 70–75 mph (113–121 km/h) (Super Sports version) |
| Frame type | Duplex cradle |
| Brakes | Drum front & rear Linked front-rear from rear pedal. |
The BSA S-Series of motorcycles, most commonly known as the BSA Sloper, were a series of motorcycles produced by the Birmingham Small Arms Company (BSA) from 1927-1935.
Launched in 1927, the 493cc overhead valve engine was slanted, and the motorcycle featured a saddle tank that enabled a low seating position, improving the centre of gravity and handling. Designated as the new S-series, whether this stood for sloper, speed or silence is unknown, but sloper became the term used by motorcyclists and hence adopted by BSA for marketing. The Sloper range remained much the same until its demise in 1935. Each model was designated with the two letters of the year produced, hence the S31 was produced in 1931.
The first models featured a 493cc (80x98mm) single ported cylinder-head, topped by a cast-aluminium enclosure for the rockers, with exposed valve springs. Alongside the cast barrel were plated tubes to cover the pushrods. Easy cam contours and wide bases on the tappets ensured no associated valve clack, meaning that the Sloper was regarded by many as one of the smoothest and quietest of sporting 500cc machines. The large crankcase accommodated both a large and heavy flywheel, and a separate oil feed tank controlled by a hand meter.
Early models had a duplex-frame and three-speed gearbox, but soon the top tube was replaced by an I-frame forging to support a new steering head. By the 1929/30 the engine carried a twin-port head, and the ohv joined by a less-popular side-valve model; these models also had extra chrome. From 1932 all were equipped by a 4-speed gearbox. From 1930 there was an optional sporting kit for £10, including a high-compression piston, hardened valves and springs, and a racing sparkplug, but the company noted that there were few buyers. The model ceased production in 1935, by which time there were only two models, an overhead-valve and a sidevalve, both of 595cc.
The large heavy flywheel and easy cams gave the Sloper a slow purposeful tick over, which was supplemented by large fishtail silencers. With a purposeful rhythm, together with its easy handling, they may have added to choice of its name. Cruising speed was 55 miles per hour (89 km/h), with a top speed of around 75 miles per hour (121 km/h).
Pictured
With its overhead valve cylinder angled forward the Sloper’s low, rakish looks were in tune with the times and have maintained a solid following ever since.
With a wet sump, saddle tank and a 90 degree valve angle, the S31-9 styling was absolutely up to the minute. What is lacking is speed (top speed was 105 kph) however its styling made up for the lack of speed indiscretion. Over 80,000 units of the BSA Sloper were sold and proved to be a company favourite. This suggested that the public’s aesthetic eye was maturing (well, at least in the 1930’s).
Although documented in Maureen Bull’s remarkable publication ‘New Zealand Motorcycle History Book One 1899 to 1931’ the early history of Neil Skeet’s BSA Sloper is not known. However, we are told it was first noticed on a railway wagon of scrap iron passing through Masterton where its reprieve was negotiated.
It passed through two owners before Neil purchased it for a modest sum. The previous owner had been using the motor in a makeshift garden tractor (a worthy task for such a strongly designed motor). Neil undertook a full restoration which resulted in this magnificent example of the BSA Sloper standard model. Fitted with a rare aftermarket rider’s instrument panel, Neil’s Sloper was well-known in the vintage club scene throughout the 60s and 70s.