BMW R51 1938 500cc ohv
Frame number: 505359 Engine number: 500790
Year: 1938 Cylinder capacity: 500 cc
Documents: swedish old road registration
video idle power: https://www.youtube.com/watch?v=6a5W2HpJUe8
video ride: https://www.youtube.com/watch?v=WGJP1dqylzU
When BMW-mounted Georg Meier became the first foreign winner of the Isle of Man Senior TT in 1939, it marked the pinnacle of pre-war success for BMW.
An important step forward in the development of BMW's long-running flat-twin occurred in 1936 with the introduction of the 494cc R5. Prior to that the BMW engine had been recognisably related to the first of its type, the 1923 R32, and like those of its (500cc) predecessors, the R5's engine dimensions were 'square' at 68mm x 68mm bore/stroke. However, the overhead-valve R5 engine broke new ground by adopting two chain-driven camshafts, a move that permitted shorter pushrods and higher revs. Maximum power increased to 24bhp at 5,800rpm. Top speed was an impressive 87mph. In 1938 the model was up-dated as the R51, gaining a telescopic front fork and plunger rear suspension, and continued in production until 1940, by which time 3,775 of these exciting sports roadsters had been sold.
Power delivered is 24 hp @ 5,600 rpm, good for a top speed of around 140 km/h. This was not an inexpensive motorcycle: in 1938 it sold for £123 at a time when Triumph's Speed Twin could be bought for under £77.
This specimen comes from Sweden. We received information from the previous owner that this motorcycle belonged to a Swedish "touring racer" Seth Lindwall. In the archive picture he is pictured with the BMW R51 together with other drivers. I can't research the story any further to see if it's about the same motorcycle. Subtext to the picture in the newspaper article was:frivilliga i finska vinterkriget, pa genomresa i Uppsala
Bilden är publicerad i Upsala Nya Tidning 10 januari 1940 med följande bildtext: "Tre av de fyra avresande frivilliga: fr. v. Seth Lindvall, Folke Nilsson och Ake Laurén.".
