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|Engine||494cc four-stroke flat-twin|
|Bore / stroke||68 mm|
|Top speed||140 km/h|
|Transmission||Single-plate dry clutch, 4-Speed manual|
|Suspension||Front telescopic forks, rear plunger|
|Weight||190 kg (wet)|
|Fuel capacity||17 L|
|Oil capacity||2 L|
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. 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.
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, which produced 35 hp (26 kW), had a compression ratio of 8.0:1.
|R51/3||R67 – R67/3|
|Design||Boxer Flat Twin|
|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)|
Media related to BMW R51 at Wikimedia Commons