BMW R90: review, history, specs

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Also called R 90-6, R 90 S, R90S
Production 1973 - 1975
Class Naked
two cylinder boxer, four-stroke
Bore / Stroke 90.0mm x 70.6mm
Compression ratio 9.5:1
Top Speed 122 mph (196 km/h)
Horsepower 65.58 HP (48.9 KW) @ 7000RPM
Torque 56.06 ft/lbs (76.0 Nm) @ 5500RPM
Transmission Gear box: 5-speed

Final Drive: shaft drive (cardan)

Clutch: dry, single plate, diaphragm spring
Suspension Front: telescopic hydraulic fork
Rear: dual adjustable shocks
Brakes Front: dual disc
Rear: expanding brake
Front Tire 3.25-19
Rear Tire 4.00-18
Wheelbase 57.72 inches (1466 mm)
Length 85.79 inches (2179 mm)
Width 29.09 inches (739 mm)
Seat Height 32.2 inches (818 mm)
Weight 232.0 kg (wet)
Oil Filter K&N KN-161[1]
Fuel Capacity 6.34 Gallon (24.00 Liters)
Manuals Service Manual

The BMW R90S was a two cylinder boxer, four-stroke Naked motorcycle produced by BMW between 1973 and 1975. It could reach a top speed of 122 mph (196 km/h). Max torque was 56.06 ft/lbs (76.0 Nm) @ 5500 RPM. Claimed horsepower was 65.58 HP (48.9 KW) @ 7000 RPM.


The engine was a air cooled two cylinder boxer, four-stroke. A 90.0mm bore x 70.6mm stroke result in a displacement of just 898.0 cubic centimeters. Fuel was supplied via a overhead valves (ohv).


The bike has a 5-speed transmission. Power was moderated via the dry, single plate, diaphragm spring.


It came with a 3.25-19 front tire and a 4.00-18 rear tire. Stopping was achieved via dual disc in the front and a expanding brake in the rear. The front suspension was a telescopic hydraulic fork while the rear was equipped with a dual adjustable shocks. The R90S was fitted with a 6.34 Gallon (24.00 Liters) fuel tank. The wheelbase was 57.72 inches (1466 mm) long.

1974 R90/6[edit]

1974 BMW R90/6

Replacements for the '/5' range, the BMW '/6' series arrived in October 1973. The newcomers were more sportily styled than the outgoing '/5's, boasting new side-panels and silencers, and totally restyled controls and instruments. Like their predecessors, the three '/6' flat twins shared an identical stroke; the 500cc model though, had been dropped in favor of the new 600cc R60/6, while at the top of the range was a new 900cc superbike: the BMW R90S. Apart from the updated styling, the presence of a disc front brake readily distinguished the '/6's, which also benefited from the new five-speed gearbox.

1975 R90/6[edit]

1976 R90/6[edit]

1973 - 1976 BMW R 90 S[edit]

1973 - 1976 BMW R 90 S 1973 - 1976 BMW R 90 S 1973 - 1976 BMW R 90 S 1973 - 1976 BMW R 90 S 1973 - 1976 BMW R 90 S

The 1973 BMW R 90 S is one of the most powerful machine designed by the German engineers up to date. It sports an air-cooled, 898cc, two cylinder boxer engine mated to a five-speed manual transmission that can produce a claimed 67 horsepower and 76 Nm of torque.

Also, it comes with features such as a dual seat, a pillion grab rail, a nose-fairing with a windscreen, a dual exhaust system, an analogue instrumentation panel, laced wheels, a telescopic hydraulic front fork, dual adjustable shocks in the rear, dual front disc brakes and a rear drum brake.

In Media[edit]


  1. 2019 K&L Supply Co Catalog. K&L Supply Co. 2019.