1940 BMW R 66 Specifications

Name: 1940 BMW R 66
Brand: BMW

All-Round • Specs last verified 13 July 2026

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1940 BMW R 66 Overview

The 1940 BMW R 66 is an all-round motorcycle built around 595 cc of displacement. Under the tank sits a Four stroke, single cylinder vertical, SV engine, a compression ratio of 6.8:1. 1940 BMW R 66 delivers 22.4 kW @ 5300 rpm of peak power. From a practical standpoint, the 1940 R 66 tips the scales at 187 kg and carries a 14-litre fuel tank. That's roughly 20.5 kg lighter than the average all-round motorcycle in our database. Scroll down for the complete 1940 BMW R 66 spec sheet covering every technical detail from suspension travel to tyre sizes.

1940 R 66 - Pros & Cons

Strengths

Capable power output: At 22.4 kW @ 5300 rpm, the R 66 holds its own against class rivals.
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

Carburetor fuelling: Carbureted engines need occasional jetting attention and can be reluctant in cold weather or at altitude compared to modern fuel-injected alternatives.

Wear Points & Servicing Notes

Heat management in traffic

R 66'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 66 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.

Suspension condition on used examples

Up front, the R 66 runs Telescopic fork and Telescopic suspension 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 Twin loop steel tubular frame - 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 66 - Buying & Maintenance Guide

What to check before buying

When inspecting a used 1940 BMW R 66, 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 66 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 66. 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 66 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.

1940 BMW R 66 - Frequently Asked Questions

What engine does the 1940 BMW R 66 have?

The 1940 BMW R 66 uses a Four stroke, single cylinder vertical, SV engine with 595 cc of displacement. It is air cooled.

How much does the 1940 BMW R 66 weigh?

The 1940 BMW R 66 weighs 187 kg. This is the manufacturer's wet figure.

How much power does the 1940 BMW R 66 make?

The 1940 BMW R 66 produces 22.4 kW @ 5300 rpm of power.

What is the fuel tank capacity of the 1940 BMW R 66?

The 1940 BMW R 66 has a 14-litre fuel tank. At around 5-6 litres per 100 km, that is roughly 233-280 km between stops.

What brakes does the 1940 BMW R 66 have?

The 1940 BMW R 66 uses ∅200mm Drum at the front and ∅200mm Drum at the rear.

What tyre sizes does the 1940 BMW R 66 use?

The 1940 BMW R 66 runs 3.50 -19 front and 3.50 -19 rear tyres. A good selection of sport, touring and all-weather rubber is available in these sizes.

What gearbox does the 1940 BMW R 66 have?

The 1940 BMW R 66 is fitted with a 4 Speed transmission.

Key Specifications

Engine

Four stroke, single cylinder vertical, SV

Power

22.4 kW / 30 hp @ 5300 rpm

Torque

Not published by manufacturer

Top Speed

Not published by manufacturer

Weight

187 kg / 411 lbs

Fuel Capacity

14 liters / 3.6 US gal

Full 1940 BMW R 66 Specifications

Year 1938-41

Make Model BMW R 66

Fuel Capacity 14 liters / 3.6 US gal

Wet Weight 187 kg / 411 lbs

Max Power 22.4 kW / 30 hp @ 5300 rpm

Displacement 595 cc / 36.3 cu in

Engine Detail Four stroke, single cylinder vertical, SV

Bore x Stroke 69.8 x 78 mm

Compression Ratio 6.8:1

Cooling System Air cooled

Fuel Induction 1 x Amal 6/420 S carburetor

Ignition Battery ignition

Starter Kick

Clutch Single plate, dry

Final Drive Shaft

Gear Ratios 1st 3.6 / 2nd 2.28 / 3rd 1. 7 / 4th 1.3

Transmission / Drive 4 Speed

Frame Type Twin loop steel tubular frame

Suspension - Front Telescopic fork

Suspension - Rear Telescopic suspension

Brakes - Front ∅200mm Drum

Brakes - Rear ∅200mm Drum

Tyres - Front 3.50 -19

Tyres - Rear 3.50 -19

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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