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Country of Manufacture:
Year: 1958
Vin #: Frame: CGM1753
Frame: Steel tubes. Single tube type with open base using engine as lower frame member
Front: Ariel/BSA type telescopic forks  
Rear: Ariel-Anstey pivoted, link action plunger system providing constant chain tension
Wheels: Chrome steel rims with spokes
Front:  7” full width single leading shoe
Rear:  8” half width single leading shoe in BSA alloy hub
Weight (dry): 460 lb (208.7 kg)
Tank Capacity: 6 gal (US), 5 gal (UK), 22.3 Litres
Horsepower: 42 hp @ 5800 rpm
Gearbox: Burman GB7 4 speed
Type: 4 stroke
Cylinders: 4 in square formation OHV
Cylinder Head: Light alloy                            
Displacement: 997 cc
Compression Ratio: 7.2:1
Ignition: coil
Clutch: Multi plate, dry
Primary & Final Drive: Chain
Carburetors: Single SU MC2
Exhaust System: 4 pipes in pairs, single muffler each side
Top Speed: 100 mph

History/Production: The Square four engine was designed by Edward Turner (later of Triumph and Daimler V8 fame) in the late 1920’s and entered production in 1930.  Basic frame and engine design concept remained essentially unchanged through the decades but major upgrades were introduced as follows: 1939 Anstey pivoted plunger rear suspension, 1948 Telescopic forks, 1949 entire engine cast in light alloy saving 30lbs,  1953/54 introduction of MK 11 model with redesigned cylinder head  and 4 exhaust pipes (2 per side), 1956 alloy cowl added to headlight and the BSA alloy front brake introduced. For the entire 28 year production period, it was always known for its exceptionally smooth running, albeit very expensive to build engine.

Production finally ended in 1958, the victim of the modern trend towards small, high-revving power units. Total production: 15,639, Mark 1: 3922 (1949-1953), Mark 11: 3828 (1953-1958)

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