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BSA Golden Flash

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BSA A10 Golden Flash
ManufacturerBirmingham Small Arms Company (BSA)
Also calledA10
Production1950–63
AssemblySmall Heath, Birmingham, UK
Predecessornone
SuccessorBSA A65 Star
Engine646 cc (39.4 cu in) air cooled twin
Bore / stroke70 mm × 84 mm (2.8 in × 3.3 in)[1]
Power35 bhp (26 kW) @ 4500 rpm[2]
Ignition typeMagneto
Transmissionfour-speed gearbox to chain drive
SuspensionTelescopic fork (front), rigid plunger swinging arm (rear)
BrakesDrum
Wheelbase1,391 mm (54.75 in)
DimensionsL: 2,100 mm (84 in)
Weight179 kg (395 lb)[3] (dry)
Fuel capacity3.5 imp gal (16 L)

The BSA Golden Flash, commonly referred to as the Gold Flash,[4] was a 646 cc (39.4 cu in) air-cooled parallel twin motorcycle designed by Bert Hopwood and produced by Birmingham Small Arms Company (BSA) at Small Heath, Birmingham. The Golden Flash was the first model in the BSA A10 series. It was available in black and chrome; but it was the distinctive golden paint scheme that gave The Golden Flash its name. Production continued until 1963,[5] when it was superseded by the BSA A65 Star.

Development

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Background and development

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Bert Hopwood served an apprenticeship under designer Val Page at Ariel. In 1936, Hopwood moved to Triumph, where he worked under Edward Turner to develop the 1937 Triumph Speed Twin. The innovative Speed Twin became the exemplar of the parallel twin engine layout for British motorcycles in the 1950s and 1960s. In April 1947 Hopwood joined Norton to design the Norton Dominator engine.

BSA, then the largest UK motorcycle manufacturer, was falling behind in the parallel-twin race. Although BSA had a parallel-twin, the BSA A7, they needed to develop the bike to remain competitive. In May 1948, the factory enticed Hopwood after only a year at Norton,[6] and he was commissioned to create a competitive BSA parallel-twin.[7][8] Launched in October 1949, Hopwood's A10 Golden Flash drew heavily from the A7 design by Page and Bert Perkins.[9]

Early Golden Flash A10s had frames with either no rear suspension, or plungers, and had a semi-unit engine and gearbox, with the gearbox bolted to the rear of the engine

The A10 was increased to 650 cc (40 cu in), with a revised alloy rocker box and cast-iron cylinder head, plus an integral manifold for the single Amal carburettor. A semi-unit gearbox meant the primary chain was adjustable via a slipper tensioner within the primary chain case. The frame was available in rear rigid format, but the more common option was plunger suspension, adopted for the export market.[10] The A10 featured a hinged rear mudguard to ease rear wheel removal. The A10 was so closely based on the A7 that it used many of its well-proven components, and this large carry-over of parts from the A7 promised greater reliability, with minimal risk of new technical problems.[9]

Early cast Golden Flash tank badge

Production

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The BSA Golden Flash was launched in a new gold colour, and 80% of production was destined for the United States. This resulted in long delivery times for British customers, who were offered the model only in black.[11]

Although never designed as a sport motorcycle, the Golden Flash was nonetheless fast for its time and competitive with the Triumph Tiger 100, achieving over 100 miles per hour (160 km/h) in tests in 1950, and covering a standing quarter mile (400 m) in under 16 seconds.[12] Its gold colour proved a marketing success, outselling Triumph's Speed Twin and 6T Thunderbird.

BSA were concerned that wear in the plunger suspension was leading to uncertain handling. In 1954 the factory adopted a swinging arm,[13] and the hinged mudguard was deleted. In a seemingly backwards step, the semi-unit gearbox was abandoned for a separate "pre-unit" item. The new design had a different primary chain adjustment, a modified clutch, and new gearbox internals.

A tuned version. the Super Flash was available in the US in 1963 - 1964. Following requests for a more powerful version from the US, the engine was turned with parts from the competition department. This was an interim measure whilst sports bike version of the A10, the Road Rocket was being developed.[14]

Late Golden Flash A10s, ca. 1961, had swinging arm frames and had a separate engine and gearbox

In 1957 an improved clutch was introduced, using 4 springs instead of six and improved friction material.[4][15]

For better reliability, the Golden Flash was upgraded in 1958 to the "thick flange" cylinders (base flange increased from 3/8" to 1/2") and larger big ends originally fitted to the Road Rocket.[16]

For 1960 the model was fitted with the 356 sports camshaft[17] and a larger (1 1/8" bore) 389 Monobloc carburettor.[18] It was renamed the "Royal Tourist" in the US.[19]

An alternator was offered as an alternative to the dynamo from 1961 to 1963, the last three years of production.

In the late 1950s, motorcycle electrical component manufacturer Lucas decided to switch production from magneto/dynamo systems to alternators/coil systems. This forced British motorcycle manufacturers to completely redesign their engines. With the launch of the new unit construction (combined engine/gearbox) BSA A50 and BSA A65, the A7 and A10 were discontinued in 1963.

See also

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References

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  1. ^ "BSA A10". Classic-British-Motorcycles.com. Retrieved 8 July 2018.
  2. ^ "BSA A10 Golden Flash - The National Motor Museum Trust". The National Motor Museum Trust. Retrieved 6 July 2018.
  3. ^ Bacon, Roy (1980). BSA Twins & Triples The Postwar A7/A10, A50/65 and Rocket III. Osprey. p. 37. ISBN 978-0-85045-368-3.
  4. ^ a b "BSA A10 Golden Flash Buyers guide". Sump. Retrieved 8 July 2018.
  5. ^ Jones, Rob; Trigwell, Ray. "BSAOC Year Listing". www.bsaownersclub.co.uk. Archived from the original on 7 October 2019. Retrieved 28 June 2018.
  6. ^ "Norton Dominator" (PDF). Archived from the original (PDF) on 28 July 2011. Retrieved 20 December 2008.
  7. ^ "1954 bsa a10sf super flash Values - Hagerty Valuation Tool®". www.hagerty.com. Retrieved 9 July 2018.
  8. ^ "The BSA Owners' Club Library archives". Archived from the original on 11 June 2008. Retrieved 20 December 2008.
  9. ^ a b Kemp, Andrew (2001). Classic British Bikes. Bookmart Ltd. pp. 120–121. ISBN 978-1-86147-058-4.
  10. ^ "Lot 031: 1950 BSA A10 Golden Flash". Motorbase. Retrieved 13 May 2008.
  11. ^ "BSA Golden Flash on test". Classic Bike Guide. May 2008.
  12. ^ "Real Classic BSA A10 (accessed 2008-05-13)". Archived from the original on 12 May 2017. Retrieved 14 May 2008.
  13. ^ Brown, Roland (2002). Classic Motorcycles. Anness Publishing. pp. 120–123. ISBN 978-1-84038-433-8.
  14. ^ "The BSA Super Flash Story". The Beezagent. 16 February 2009. Retrieved 7 July 2018.
  15. ^ Assoc, American Motorcyclist (1957). American Motorcyclist. American Motorcyclist Assoc.
  16. ^ "Pre-Unit A Group". www.draganfly.co.uk. Retrieved 7 July 2018.[permanent dead link‍]
  17. ^ "Pre-Unit A Group". www.draganfly.co.uk. Retrieved 7 July 2018.[permanent dead link‍]
  18. ^ "Carburettor Settings – B.S.A" (PDF). Draganfly Motorcycles. Retrieved 7 July 2018.
  19. ^ American Motorcyclist. American Motorcyclist Assoc. 1959.

Further reading

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  • Bacon, Roy (1980). BSA Twins & Triples The postwar A7/A10, A50/65 and Rocket III. Oxford: Osprey Publishing.
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