BMW R51/3
A 1952 R51/3 – note the half-width brakes before 1954
ManufacturerBMW
Production1951-5
Engine494cc four-stroke flat-twin
Bore / stroke68 mm
Compression ratio6.3:1
Top speed140 km/h
Power24 hp
Ignition typeMagneto
TransmissionSingle-plate dry clutch, 4-Speed manual
SuspensionFront telescopic forks, rear plunger
Brakes200mm drums
Wheelbase1400mm
DimensionsL: 2130mm
W: 790mm
H: 985mm
Weight190 kg (wet)
Fuel capacity17 L
Oil capacity2 L
Fuel consumption4.5L/100KM
1951 R51/3 at the BMW Museum
1955 BMW R67/3
An R51/3 has eight round cylinder fins (left); the R67-R67/3 have nine larger and pointed cylinder fins (right)
Note the exposed driveshaft and plunger rear suspension

The BMW R51/3 was BMW's second post-World War II 500 cc motorcycle, following the briefly produced R51/2. It featured a flat-twin engine and exposed drive shaft.[1] In 1951, the R51/3 succeeded and modernized the 1950 R51/2, which was essentially a pre-war design that was produced after the war. The 600 cc R67, R67/2, and R67/3 series and the more sporting R68 model also followed the R51/2.

History

Following World War II, Germany was precluded from producing motorcycles of any sort by the Allies. When the ban was lifted, in Allied-controlled Western Germany, BMW had to start from scratch. There were no plans, blueprints, or schematic drawings. Company engineers had to use surviving pre-war motorcycles to create new plans. In 1948, it introduced the 250 cc R24, which was essentially a pre-war R23, complete with rigid rear end.

When larger machines were permitted, BMW introduced its R51/2 in 1950, a model that was in production for only one year and that was essentially a pre-war BMW produced after the war. The R51/3 was then introduced in 1951 for a production run of four years.

The 600 cc R67, sister model to the R51/3 and almost identical visually, was also introduced in 1951, but it went through two revisions. The more powerful R67/2 came out one year later and was replaced in 1955 by the R67/3, which was in production through the 1956 model year.

In 1952, BMW introduced the 600 cc R68,[2] which produced 35 hp (26 kW), had a compression ratio of 8.0:1.

Technical data

Front view of an R51/3
R51/3 R67 – R67/3
Design Boxer Flat Twin
Engine Four-stroke OHV
Model Years 1951–1955 1951–1956
Bore 68 mm / 2.68 in 72 mm / 2.83 in
Stroke 68 mm / 2.68 in 73 mm / 2.87 in
Displacement 494 cc (30.1 cu in) 594 cc (36.2 cu in)
Power 24 hp (18 kW) @ 5800 rpm 26 hp (19 kW) / 28 hp (21 kW) @ 5500 rpm
Compression Ratio 6.3:1 5.6:1 / 6.5:1
Top Speed 140 km/h (87 mph) 150 km/h (93 mph)
Curb Weight 190 kg (419 lb)
Gross Vehicle Weight 355 kg (783 lb)
Fuel Tank Capacity 17 L (3.7 imp gal; 4.5 US gal)

See also

References

  1. ↑ "R51/3 data sheet". Archived from the original on 2014-10-31. Retrieved 2012-07-05.
  2. ↑ "BMW R68 Data". Archived from the original on 2014-08-08. Retrieved 2012-07-03.

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