|Engine||air-cooled, four-stroke, single vertical cylinder|
|Bore / Stroke||83.8mm x 83.8mm|
|Horse Power||13.95 HP (10.4 KW) @ 4000RPM|
|Transmission||Gear box: 4-speed, manual |
Final Drive: shaft
|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)|
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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.
The bike has a 4-speed, manual transmission. Power was moderated via the dry, single plate.
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.