BSA A65 Star Twin (1962-72)

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The BSA A65 Star Twin motorcycle was produced between 1962 and 1972 with a 654cc four-stroke parallel twin cylinder engine, an Amal monobloc carburetor, and twin stainless steel exhausts. It had a compression ratio of 8.0:1, dry sump lubrication, and a 4-speed transmission with a chain final drive. The bike had a steel tubing cradle frame, telescopic forks with coil spring-hydraulically damped front suspension, and coil spring-hydraulically damped rear suspension. Front and rear drum brakes were used, with 8-inch and 7-inch drums respectively. The wheels were steel with wire spokes, and the bike had a WM2-18 front and rear rim. The fuel capacity was 18 liters in Europe and 9 liters in the US, with an average consumption of 4.7L/100km or 50mpg. The bike had a top speed of 160km/h or 100mph and came in two colors: blue and ruby red. Prior to 1966, the bike had a 6V, 13 AH Lucas RM19 alternator, and post-1966, it had a 12V, 9 AH Lucas RM19 alternator. The bike had a kick start and weighed 176kg or 390lbs. The dimensions were 2060mm in length, 711mm in width, and 1010mm in height with a wheelbase of 1372mm, ground clearance of 178mm, and seat height of 813mm. The engine produced a maximum power of 40 kW or 54 hp at 4500 rpm, and the bike had a Champion N4 spark plug with a 0.5mm gap, 14mm diameter thread, and 19mm reach.

Technical specifications:

Make Model: BSA Star Twin / Royal Star

Year: 1962 – 72


Engine: Four stroke, parallel twin cylinder, OHV, 2 valves per cylinder
Capacity: 654 cc / 39.9 cub in.
Bore x Stroke: 75 x 74 mm
Carburetor: Amal monobloc 389/67
Cooling System: Air cooled
Compression Ratio: 8.0:1
Lubrication: Dry sump
Engine Oil: SAE 20W/50
Oil Capacity: 3 L / 5 pints / 0.79 US gal
Exhaust: Twin, stainless steel
Ignition: Twin coil
Spark Plug: Champion N4, 0.5 mm / 0.02 in gap, 14 mm dia thread, 19 mm reach
Battery: Prior 1966: 6V, 13 AH, Lucas RM19 alternator Post 1966: 12V, 9 AH, Lucas RM19 Alternator
Starting: Kick start
Max Power: 40 kW / 54 hp @ 4500 rpm

Clutch: Multi-plate with bult-in cush drive
Transmission: 4 Speed
Final Drive: Chain
Gear Ratio: 1st 11.49 / 2nd 7.32 / 3rd 5.24 / 4th 4.58:1
Frame: Steel tubing, cradle
Front Suspension: Telescopic forks with coil spring – hydraulically damped
Rear Suspension: Coil spring/hydraulically damped
Front Brakes: 20.32 cm / 8 in., drum
Rear Brakes: 17.78 cm / 7In., drum
Wheels: Steel, wire spokes
Front Rim: WM2-18
Rear Rim: WM2-18
Front Tyre: 3.25 x 18 in., ribbed
Rear Tyre: 3.50 x 18 in., K70
Dimensions: Length: 2060 mm / 81.0 in. Width: 711 mm / 28.0 in. Height: 1010 mm / 39.8 in.
Wheelbase: 1372 mm / 54.0 in.
Ground Clearance: 178 mm / 7.0 in.
Seat Height: 813 mm / 32 in.
Wet Weight: 176 kg / 390 lbs
Fuel Capacity: Europe:18 L / 4.8 US gal US: 9 L / 2.4 US gal

Average Consumption: 4.7 L/100 km / 21.3 km/l / 50 mpg
Top Speed: 160 km/h / 100 mph
Colours: Blue, Ruby red
Review: Wikipedia, Classic and Race Bike

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