BMW R4: history, specs, pictures

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BMW R 4
BMW R4
Manufacturer BMW
Production 1932 - 1937
Class Classic
Engine air-cooled, four-stroke, single vertical cylinder
Bore / Stroke 83.8mm x 83.8mm
Compression ratio 5.7:1
Top speed 59 mph (95 km/h)
Horse Power 13.95 HP (10.4 KW) @ 4000RPM
Fuel system carburettor. sum ck 3/500 fr
Transmission Gear box: 4-speed, manual

Final Drive: shaft

Clutch: dry, single plate
Suspension Front: parallelogram fork
Rear: hard-tail, sprung seat
Brakes Front: 160mm drum
Rear: 160mm drum
Front Tire 3.50 x 26
Rear Tire 3.50 x 26
Weight  (dry), 137.0 kg (wet)
Fuel consumption 3.50 litres/100 km (28.6 km/l or 67.21 mpg)
Manuals Service Manual
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The BMW R4 was a air-cooled, four-stroke, single vertical cylinder Classic motorcycle produced by BMW in 1932. Claimed horsepower was 13.95 HP (10.4 KW) @ 4000 RPM.


BMW R4

BMW produced 15,200 R4 motorcycles using innovative mass production techniques, setting new standards of design and quality. Pressed steel frame and components were quick and easy to stamp out and assemble, reducing manufacturing costs.

Introduced in 1932 and intended to bridge the gap between the 'budget' BMW R2 198cc single and the expensive twins, the R4 looked much like the former, whose channel-section steel frame and running gear it used almost unaltered. The 398cc overhead-valve engine featured enclosed valve gear and produced 12bhp, gaining an extra two horsepower in 1933 when the BMW R4 was updated to Series 2 specification with revised styling and a four-speed gearbox. A new cylinder head, tidier engine casings and changes to the toolbox and generator locations were introduced as the rugged R4 - a favourite with police forces and the German Army - progressed through to Series 5 before production ceased in 1936.

Engine

A 83.8mm bore x 83.8mm stroke result in a displacement of just 498.0 cubic centimeters.

Drive

The bike has a 4-speed, manual transmission. Power was moderated via the dry, single plate.

Chassis

It came with a 3.50 x 26 front tire and a 3.50 x 26 rear tire. Stopping was achieved via 160mm drum in the front and a 160mm drum in the rear. The front suspension was a parallelogram fork while the rear was equipped with a hard-tail, sprung seat.

1932 - 1937 BMW R 4

The 1932 BMW R 4 has, at its heart, an air-cooled, four-stroke, 498cc, single vertical cylinder engine mated to a four-speed manual transmission that can produce a claimed 14 horsepower at 4000 rpm. This classic machine had standard features such as laced wheels, full fenders, a hard-tail rear suspension with a sprung seat, a parallelogram front suspension, a large headlight, a rear luggage rack and an exhaust system with a large-diameter muffler.


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