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1973 BMW R 90S Overview
The 1973 BMW R 90S is an all-round motorcycle built around 898 cc of displacement. Under the tank sits a Four stroke, two cylinder horizontally opposed Boxer, pushrod operated 2 valves per cylinder engine, a compression ratio of 9.5:1. 1973 BMW R 90S delivers 48.8 kW @ 7000 rpm of peak power and 76 Nm @ 5500 rpm of torque. The factory-quoted top speed stands at 200 km/h, making it a capable performer in its class. From a practical standpoint, the 1973 R 90S tips the scales at 215 Kg, carries a 24-litre fuel tank, offers a seat height of 820 mm and spans a 1465 mm wheelbase. That's roughly 7.5 kg heavier than the average all-round motorcycle in our database. Scroll down for the complete 1973 BMW R 90S spec sheet covering every technical detail from suspension travel to tyre sizes.
1973 R 90S - Pros & Cons
Strengths
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Strong power output: 1973 BMW R 90S makes 48.8 kW @ 7000 rpm with 76 Nm @ 5500 rpm of torque - competitive figures for its class.
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Large fuel range: The 24-litre tank is generously sized, translating to extended range between stops - ideal for touring or longer commutes.
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Low-maintenance final drive: Shaft final drive means no chain to clean, lube or adjust - meaningfully less routine maintenance than a chain-driven equivalent.
Considerations
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Carburetor fuelling: Carbureted engines need occasional jetting attention and can be reluctant in cold weather or at altitude compared to modern fuel-injected alternatives.
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Tall seat height: The 820 mm seat height will challenge shorter riders - tiptoeing at low speeds is something to factor into your decision.
Wear Points & Servicing Notes
Heat management in traffic
R 90S's air-cooled design means engine-bay temperatures build up more in stop-start traffic than on a liquid-cooled equivalent - a function of the cooling method itself, not a defect. Mesh riding gear and avoiding prolonged idling help in hot climates.
Carburetor maintenance
The R 90S uses carburetion rather than fuel injection, which means jetting is altitude- and temperature-sensitive and benefits from a clean-and-rejet after extended storage or an exhaust change.
Brake disc and pad wear
The 2 x ∅260mm discs, 1 piston caliper front brake gives strong, progressive stopping power. Disc thickness and pad depth are worth checking at every tyre change, since worn pads can score the disc surface.
Suspension condition on used examples
Up front, the R 90S runs Telescopic fork with hydraulic shock absorber and Long swinging arm with adjustable strut at the rear. On a used example, check fork seals for weeping oil and test the rear linkage for play - seals are a relatively cheap fix but useful when negotiating price.
Final drive maintenance
Final drive is by shaft - no chain or belt maintenance at all, though the drive-shaft oil should be changed on the manufacturer's interval.
Frame & chassis check
The frame is Double-loop tubular frame with bolt-on rear section - worth a visual check for corrosion or impact damage around the head-stock and swingarm pivot on any used example, since frame damage is far costlier to fix than any service item.
R 90S - Buying & Maintenance Guide
What to check before buying
When inspecting a used 1973 BMW R 90S, start with the basics: check the service book for oil change frequency, inspect the chain and sprockets for wear, and look for oil seepage around the engine casings and rocker covers. A cold start test is invaluable - a well-maintained R 90S should fire up cleanly and settle to a smooth idle within a few seconds.
Oil and filter changes
Regular oil changes are the single most important maintenance task on any R 90S. Stick to the manufacturer's interval - typically every 6,000 km or once a year, whichever comes first. Always use the correct viscosity grade as specified in the owner's manual.
Carburetor upkeep
Keep the carburetors clean and free of deposits. If the R 90S has been stored, strip and clean the carb float bowls before attempting to start it. Pilot jets are the first to block and the last to be checked - always include them in any carb rebuild.
1973 BMW R 90S - Frequently Asked Questions
What engine does the 1973 BMW R 90S have?
The 1973 BMW R 90S uses a Four stroke, two cylinder horizontally opposed Boxer, pushrod operated 2 valves per cylinder. engine with 898 cc of displacement. It is air cooled.
What is the top speed of the 1973 BMW R 90S?
The 1973 BMW R 90S has a factory-quoted top speed of 200 km/h. Real-world speeds vary depending on rider weight, conditions and state of tune.
How much does the 1973 BMW R 90S weigh?
The 1973 BMW R 90S weighs 215 Kg. This is the manufacturer's wet figure.
How much power does the 1973 BMW R 90S make?
The 1973 BMW R 90S produces 48.8 kW @ 7000 rpm of power and 76 Nm @ 5500 rpm of torque. These are peak figures.
What is the fuel tank capacity of the 1973 BMW R 90S?
The 1973 BMW R 90S has a 24-litre fuel tank. At around 5-6 litres per 100 km, that is roughly 400-480 km between stops.
Is the 1973 BMW R 90S suitable for shorter riders?
The 1973 BMW R 90S has a seat height of 820 mm. This is towards the tall end of the spectrum and will require most riders under 175 cm to tiptoe at stops.
What brakes does the 1973 BMW R 90S have?
The 1973 BMW R 90S uses 2 x ∅260mm discs, 1 piston caliper at the front and ∅200mm Drum at the rear.
What tyre sizes does the 1973 BMW R 90S use?
The 1973 BMW R 90S runs 3.25 - H19 front and 4 - H18 rear tyres. A good selection of sport, touring and all-weather rubber is available in these sizes.
What gearbox does the 1973 BMW R 90S have?
The 1973 BMW R 90S is fitted with a 5 Speed transmission.
Key Specifications
Engine
Four stroke, two cylinder horizontally opposed Boxer, pushrod operated 2 valves per cylinder.
Power
48.8 kW / 67 hp @ 7000 rpm
Torque
76 Nm / 7.6 kgf-m / 55 ft-lb @ 5500 rpm
Top Speed
200 km/h / 124 mph
Fuel Capacity
24 Litres / 6.3 US gal
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Full 1973 BMW R 90S Specifications
Year
1973 - 76
Make Model
BMW R 90S
Total Produced
17465 units
Seat Height
820 mm / 32.2 in
Wheelbase
1465 mm / 57.67 in
Ground Clearance
165 mm / 6.49 in
Height
1210 mm / 47.63 in
Length
2180 mm / 85.82 in
Width
740 mm / 29.13 in
Fuel Capacity
24 Litres / 6.3 US gal
Wet Weight
215 Kg / 473 lbs
Displacement
898 cc / 54.8 cu in.
Engine Detail
Four stroke, two cylinder horizontally opposed Boxer, pushrod operated 2 valves per cylinder.
Bore x Stroke
90 x 70.6 mm
Compression Ratio
9.5:1
Cooling System
Air cooled
Fuel Consumption
5.1 L/100 km / 19.6 km/l / 46 mpg
Fuel Induction
2 x slide Dell'Orto PHM 38 carburetors
Ignition
Kettering
Lubrication
Gear driven pump
Starter
Electric
Clutch
Dry single plate, with diaphragm spring
Final Drive
Shaft
Gear Ratios
1st 4.40 / 2nd 2.86 / 3rd 2.07 / 4th 1.67:1 / 5th 1.50:1
Transmission / Drive
5 Speed
Frame Type
Double-loop tubular frame with bolt-on rear section
Suspension - Front
Telescopic fork with hydraulic shock absorber
Suspension - Rear
Long swinging arm with adjustable strut.
Wheel Travel - Front
208 mm / 8.1 in
Wheel Travel - Rear
125 mm / 4.9 in
Charging System
12V 280W alternator
Brakes - Front
2 x ∅260mm discs, 1 piston caliper
Brakes - Rear
∅200mm Drum
Tyres - Front
3.25 - H19
Tyres - Rear
4.00 - H18
Wheels - Front
1.85 - B19
Wheels - Rear
2.15 - B18
Specifications are compiled from manufacturer documentation and cross-referenced
technical sources, and corrected on an ongoing basis.
Spot an error? Let us know.
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