BSA 500cc

1927 BSA 500cc single (pdf)

Big Slow and Awkward. That was the reputation of Birmingham Small Arms' range of dependable but boring motor cycles. But this 1927 Sloper is some­thing else. Fitted with a TT carburettor, the engine gulps a petrol-air mix with no consideration for fuel economy and packs a punch that has the back wheel digging into the tar­mac as it powers the 500cc single towards the  horizon. So why didn't BSA make more of its sport­ing capabilities?

Compared with the pioneers, Ariel, Matchless, P&M and Royal Enfield, BSA were latecomers to motor cycling. Indeed, despite at least one brief early involvement with two wheelers, and an on-going commitment to bicycle components, it was not until 1908 and a successful takeover of the famous Eadie company of Redditch that BSA finally became established bicy­cle makers.

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From bicycles to motor cycles was an obvious step. Albert Eadie, who had joined the board of BSA, was put in charge of motor cycle development in 1909. Under him, on the practical side, were Charles Hyde — who had worked for Eadie before spending several years as works manager for James — and Frank Baker. He had studied production engineer­ing in America before founding his own Precision Manufacturing Company in 1906 to produce cycle fittings.

Baker worked for BSA as a consultant. Once his work there was completed, he branched out into the manufacture of Precision engines. By the outbreak of war in 1914 Precision had overtaken in popularity the old established JAP company.

It was a measure of the good sense of both Hyde and Baker that they avoided many problems for BSA by making a faithful copy of the most successful motor cycle engine of the time, the 85 x 85mm 499cc 3½hp Triumph. The BSA was displayed at the Motor Cycle Show, newly located at Olympia. Priced at £50 in single speed form, and with a clutch in the rear hub costing an extra £6, it was a run­away success.

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Later, a BSA made three speed gearbox with an internal metal to metal clutch was introduced, and the stroke of the engine lengthened to 98mm to give a capacity of 557cc. The original engine dimensions were retained for a TT model.

At that time, a TT model did not necessari­ly imply any direct connection with the Isle of Man. BSA did achieve some impressive results at Brooklands, and in 1913 entered a team of seven in the Senior TT. These men were riding virtually standard machines, in the hope of completing a demonstration of high speed reliability. Alas, only one BSA fin­ished, in a lowly 17th place. In 1914 seven standard machines were entered with happi­er results – only two retired, and the best finisher was 12th.

That year's races were notable for two things, one being the compulsory wearing of ACU approved crash helmets. The other was the large number of purpose built racers, many of them bearing little resemblance to standard productions. So disturbed was the ACU by this trend that the regulations for 1915 stipulated that all entries should be based on catalogued models.

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Of course the 1915 races never took place at all. Europe was at war, and post war the stipulation was forgotten. But it is more than likely that 1914 sowed the seeds of BSA's dis­astrous TT entry of 1921.

BSA spent 18 months and £10,000 on the design and development of a radical new ohv racer with which they intended to sweep the board. Notable features were a steeply slop­ing cylinder with a strange updraught induc­tion system, a triangulated duplex frame, and an ultra low riding position. With six Senior TT entries (and no less than 14 machines in the Island) the BSAs received tremendous attention and publicity.

This made the subsequent fiasco all the more degrading for the company. None of the BSAs lasted for more than two laps, and humiliation was complete. Back home in Birmingham several heads rolled, and the Board of Directors vowed that never, ever again, would BSAs go road racing.

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Even so, for a company whose business was acknowledged to be well made but oh ­so-sober machinery for the bread and butter market, BSA rarely seemed to be for too long without a sporting model in the range. In 1924 there was a cracking little 350cc ohv model. And dining the Thirties the Star series was very popular. The Empire Star, Blue Star and Blue Star Special ranges were to culmi­nate in 1938 in the all alloy 85 x 85mm 499cc Gold Star.

Few people today realise that this series began with a model that is now widely regarded as the very epitome of the flexible slogging sidecar machine, the famous Sloper. Yes, the long stroke 80 x 98mm 493cc Sloper, designed by Harold Briggs and long term BSA stalwart F W Hulse, was around in 1926 and sold as an uncompromising super-sports machine with the expectation that it would be used in racing.

Orthodox in conception, the Sloper never­theless incorporates some interesting points. The inclined cylinder — which was to set a short lived but intense fashion — suppressed vibration, and the steeply sloping frame tubes allowed a fashionably low riding position. Indeed, the top of the Terry or alternative Lockie super sports saddle was only 24in from the ground. BSA's own girder front fork was used with the sturdy duplex frame. There were 7in brakes front and rear. A departure for BSA was a saddle tank ­rather slab sided to modern eyes — contain­ing two gallons of petrol. Overall weight was a remarkably low 300lb.

The cylinder and head were cast iron and the nickel steel valves were disposed at 90 degrees in a fully hemi­spherical combustion chamber. Light alloy pushrods and valve gear were enclosed, though the ends of the rockers and valve springs were in the open air.

The lubrication sys­tem was semi dry sump, oil being carried in a large container cast integrally with the crankcase. A submerged gear pump forced oil into the caged two row roller big-end, after which it was distributed by splash, and as oil mist. Surplus oil was picked up by the fly­wheels and returned to the integral sump by a scraper.

BSA 500cc Sloper classic British motorcycleThere was an indicator on the delivery side of the pump to show that oil was circulating, and the rate of flow could be regulated by a control on the crankcase which, said the brochure, could "easily be reached from the saddle". An optional extra was a separate oil tank bolted to the saddle tube, with a foot pedal operated pump supplying oil to the rear of the cylinder wall "for long distance races".

There was a genuine Lucas racing magneto set behind the cylinder and an Amac TT car­burettor. A 2in exhaust led the gases into a large capacity silencer that not only pro­claimed 'Brooklands' in its appearance, but which actually conformed to the regulations in force at the famous Weybridge track.

Steel flywheels were standard in an age when most manufacturers made do with cast iron. But there was more. An alternative high compression piston was supplied at no extra cost, as were a racing sparking plug and high ratio engine sprocket The three speed con­stant mesh gearbox could be supplied with close ratios on request But surely the clinch­er was the offer — for an extra £5 — to sup­ply an engine guaranteed to make 25 bhp at 5250 rpm rather than the adequate enough standard 18 bhp.

Nor were the public backward at taking advantage of this offer, whether or not they intended to go racing. So popular were these tuned engines that some unknown storekeep­er at BSA stencilled a star in quick drying red paint on the crankcase to distinguish them. So a name was born: the Red Star designa­tion entered the catalogue during 1927.

The 500cc Sloper made no great impact as a genuine racing motor cycle. What success­es BSA did advertise were almost all in long distance Colonial events. And, almost unbe­lievably, neither The Motor Cycle nor its rival Motor Cycling published a road test of the Sloper in solo trim. Indeed the only test pub­lished between the Sloper's announcement and its disappearance at the end of 1932 was with a sidecar, late in 1927. The Motor Cycle was enthusiastic enough, and gave the com­bination's top speed as a little more than 55 mph, but the test was not very informative.

During the Sloper's lifetime, the BSA single altered little, except in detail. In 1929, twin exhausts became an option in accordance with another transient fashion. A year later the Sloper – along with most other BSA models — featured a new frame with a forged steel I-section backbone instead of a top tube.

The Sloper was a trendsetter, and, impor­tantly for BSA's fortunes at a difficult time, a best seller. With it, BSA put behind them dummy belt rim brakes, flat tanks and the spindly looks of the vintage era.

"When I was in a demanding and stressful job," says Alan Fisher, "owning a motor cycle and working on it in the evenings helped to keep me sane." Now his own master – having taken early retirement – Alan can potter to his heart's content in his bright and well equipped workshop.

Until 1993, he had for several seasons been riding a 1925 250cc side-valve Raleigh in vin­tage events. "It's a good little bike," he says, "but a bit on the small side for a chap of 17 stones weight. What's more, my wife Rose was as keen as I was, but there was no way that the poor little Raleigh was going to carry two of us."

Alan looked round for something a bit more power­ful. A friend from Hastings, Bill Pile, mentioned he had a 1927 500cc BSA Sloper for sale. Bill had spent a lot of money having it restored.

"As soon as I saw it, I liked it," says Alan. "It had a purposeful look. Close examination showed that everything was as it should have been, with a couple of small exceptions. When Alan Fisher first rode the Sloper the steering felt uncertain and it did not take long to discover that the head races were slack That was soon put right and effected a total cure.

Over the years the cam spindles had worn, and someone had compensated for this by cutting strips of thin shim steel and wrapping them round the spindles. "I'm sure that miss­ing this detail was a genuine oversight," says Alan, "because in all other respects the restoration work was first class."

That the engine is in good mechanical order is shown by the ease with which it can be brought to life by a single prod. Retard the ignition and it settles down to a slow and steady tickover. The exhaust note is surprisingly subdued considering the sporting silencer, so that the modest mechanical noise — piston slap when cold, and a dis­tinct rap from the closing valves – is noticeable, though by no means offen­sive.

The clutch takes up smoothly and the gear ratios are well chosen. A hand change takes a bit of getting used to, but the Sloper is one of the better ones, operating in a well defined gate on the side of the petrol tank After Alan Fisher's attention, the brakes are smooth and positive, inspiring confidence.

The engine performance is something of a surprise. With its long stroke, and distinctly heavy looks — not to speak of its reputation as a sidecar hauler — one imagines that the BSA will have a lot of torque and slog along in a lazy fashion. To be sure, the engine is flexible, but it is also very willing to rev. Vibration is conspicuously absent

I made no attempt to explore the Sloper's sporting potential, leaving that to a younger man. Editor Phillip Tooth found gearchange slick and quick, and had the BSA hurtling along at 70 mph in no time at all. With the weight slung low down, he could fling the Sloper into bends or ride hands-off down country roads with complete confidence. And hauling on the massive brakes got the wired-on tyres squealing. Ahead of its time in its specification, a trendsetter for the rest of the industry, the BSA Sloper is no slouch. bike  View original article

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