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BMW Motorcycles
BMW R90S

BMW R90S 1973-1976

Engine
Configuration

BMW-1973-R90S-Engine-Db.jpg
BMW R90S Engine

Horizontally opposed air-cooled twin, pushrod operated valves, 2 per cylinder Lubrication Gear driven pump
Bore & Stroke 90 x 70.6 mm Ignition Kettering
Capacity 898 cc Charging system 12v  280w alternator
Compression Ratio 9.5 : 1 Starter Electric starter 0.5 hp
Maximum Power 67 DIN hp at 7000 rpm Transmission Gear driven primary drive, 3.00:1 bevel final drive (optional 2.91:1)
Maximum Torque 55 ft/lb (7.6 mkg) at 5500 rpm Gearbox 1st 4.40: 1 
2nd 2.86:1 
3rd 2.07:1 
4th 1.67:1 
5th 1.50:1
Fuel Dell'Orto PHM 38mm slide type carburettors 
Micronic air filter
Clutch Cable operated single plate dry clutch
Chassis
Frame Steel main and bolt-on subframe Wheels 1.85 x 19 front 
2.15 x 18 rear 
Spoked alloy rims
Dimensions  Weight: 215 kg wet 
Wheelbase: 1465 mm 
Length: 2180 mm 
Seat Height: 820 mm
Tyres 3.25 H 19 front 
4.00 H 18 rear 
Front Suspension Hydraulic telescopic  Brakes Front: 260 mm stainless undrilled discs with floating single piston calipers 
Rear: 200 x 30 mm drum
Rear suspension Boge dual dampers, springs adjustable for pre-load  Fuel Capacity 24 Litres (5 1/4 Imperial gallons)
including 2.5l reserve
Performance
Top Speed Upright: 195 kph (121 mph) 
Prone: 200 kph+ (125 mph+)
Fuel Economy 55.7 mpg (Imp.) at 68 mph
Acceleration Standing 400m: 13.3 sec 
Standing 1000m: 25.3 sec 
0-62.5 mph: 4.8 sec 


Images from the 1973 BMW Factory Brochure

R90S Specifications were the same throughout the model run

The cockpit remained basically unchanged throughout the R90S model run. The fairing was made of a composite resembling carbon fibre, as were the sidecovers.

Initially, switches were of the pushbutton variety, similar to those used on the stroke five models. Later renditions of the R90S had more modern switchblocks.