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BMW R51/3


The 'BMW R51/3' was BMW's first modern postwar 500 cc motorcycle. It used BMW's time-tested boxer engine layout and exposed driveshaft. The R51/3 succeeded and modernized the 1950 R51/2, which was essentially a prewar design that was produced after the war.

Contents
History
Technical data
Gallery
See also
External links

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 Aktiengesellschaft (AG) had to start from scratch. There were no plans, blueprints, or schematic drawings. Company engineers had to use surviving prewar 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 [1] in 1950, a model that was in production for only one year and that was essentially a prewar 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 R67/2, with 2 hp (2 kW) more, 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] [3]. With 35 hp and a compression ratio of 8.0:1, this was the first BMW production motorcycle that could reach and pass 100 mph (160 km/h).

Technical data


The engine of the R51/3's predecessor, the 1950 R51/2, had an exposed generator, no magneto, and split valve covers

Compare the clean, unit-cast R51/3 engine above to that of the R51/2 above


 R51/3R67 - 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 in³594 cc / 36 in³
'Power'24 hp26 hp / 28 hp
'@ RPM'5,8005,500
'Compression Ratio'1:6.31:5.6 / 1:6.5
'Top Speed'87 mph (140 km/h)93 mph (150 km/h)
'Curb Weight' 419 lb (190 kg)
'Gross Vehicle Weight' 783 lb (355 kg)
'Fuel Tank Capacity' 4.5 US gallons (17 litres)


Gallery




See also



BMW Motorcycles

BMW R60/2

BMW R75/5

BMW R1200RT

Motorcycle Forks



German R51/3 Wikipedia page translated into English

External links



''BMW R51/3''

''1952 BMW R51/3''

''1954 BMW R68''

''R51/3 Technical Specifications''

''1952 BMW R51/3 & R67/2 Technical Pages'' from an owner's manual

''BMW R51/3 Photos''

BMW R51/2, R51/3, R67, R67/2, & R67/3 engine numbers

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