1957 BSA A10
Pre-Unit 650 Twin

1957 BSA A10 BACKGROUND
BSA's A10 was the 650 version in it's twin cylinder heavyweight line. The 500cc version was called the A7. Following Triumph's success with its seminal 500 Speed Twin, after the war, BSA and most of the rest of the British motorcycle industry followed with their own vertical twins. BSA was first to respond in 1946 (the first year of civilian production following World War II) with the A7, Norton and Matchless followed in 1949. But by 1950, Triumph had bumped the displacement if its twin up to 650cc, and once again most of the rest of the British motorcycle industry followed suit. BSA punched the A7 out to a 650 in 1950 also, giving it the A10 name. Performance and reliability were added incrementally over several model years. As problems arose, BSA dealt with them in a slow, but steady process of development. By this time the 1957 BSA A10, the entire BSA twin line was experiencing great success in the marketplace. The 1950s truly were BSA's heyday. Good thing too, because by the 1960s, the whole thing had turned around on them, and BSA struggled throughout most of that decade until they closed their doors in 1972. Many people blame the replacement of BSA's non-unit twins, the A10 and the A7 with the unit-construction A50 and A65 in 1962 as the turning point. The timing certainly lines up.

1957 BSA A10 SPECIFICATIONS

Engine type

Displacement

Bore & Stroke

Compression

Carburetor

Primary drive

Clutch

Final drive

Gearbox

Ratios, overall:

1st, Bottom

2nd

3rd

4th, Top

Wheelbase

Seat height

Ground clearance

Brakes, front

Brakes, rear

Tires, front

Tires, rear

Fuel capacity

Curb weight

PERFORMANCE

1/4 mile

Top speed

Air-cooled OHV vertical twin

646cc

70mm X 84mm

8.0:1

1- Amal

1/2" X.305 single-row chain

Multi-plate, wet

5/8" X 3/8" chain

BSA constant-mesh 4-speed, foot shift


11.68:1

7.95:1

5.48:1

4.53:1

56.5"

32", unladen

5.5", unladen

7.0" SLS drum

7.0" SLS drum

3.25" x 19"

3.50" x 19"

4.0 gal

450 lbs


15.0 sec @ 85 mph

105 mph



MORE BSA PAGES:
BSA Motorcycles
..... BSA Gold Star
..........1939
..........1953
..........1954
..........1961
..........1962
..... BSA A7 (pre-unit 500)
..........1952
..........1955
..... BSA A10 (pre-unit 650)
..........1951
..........1954
..........1957
..........1958
..... BSA A65 (unit-construction 650)
..........1962
..........1963
..........1964
..........1965
..........1966
..........1967
..........1968
..........1969
..........1970
..........1971
..... BSA Rocket 3 (750 triple)
..........1969
..........1971
..... BSA Bantam


Check out these BSA BOOKS





BSA Motorcycles: The Final Evolution



The BSA Gold Star: Motorcycle History



Illustrated Bsa Buyer's Guide (Motorbooks International Illustrated Buyer's Guide)



Bsa Twin Restoration



BSA Unit Singles: The Complete Story including the Triumph Derivatives



Bsa Motor Cycles: Since 1950 (British Motor cycles since 1950)



BSA Unit Twins



BSA 500 & 650 Twins: The Essential Buyer's Guide



Triumph and Bsa Triples



How to Restore Triumph Trident T150/T160 & BSA Rocket III: YOUR step-by-step colour illustrated guide to complete restoration (Enthusiast's Restoration Manual)




For more like these, visit our BSA BOOK STORE






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Last updated 11/21/17

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