Motorcycles | 7 March 2016BMW Motorcycles: 1970 R75/5, R60/5, and R50/5 Share article facebook twitter google pinterest BMW has made some amazing automotive, technological, and aesthetic advancements throughout its history, many of which are showcased in Ian Falloon’s new book, The Complete Book of BMW Motorcycles: Every Model Since 1923, the ultimate resource for the fantastic motorcycles built by Germany’s leading motorcycle manufacturer. The following excerpt from Falloon’s book on the 1970 R75/5, R60/5, and R50/5 is a sure favorite. This bike not only reminds us of the amazing manufacturing of BMW motorcycles, but it’s also a nostalgic reminder of the 1970 aesthetic. 1970 R75/5, R60/5, and R50/5 The early R50/5 was virtually indistinguishable from the R60/5 and R75/5. This is the 1970 US R50/5 with higher handlebars. BMW Group Archives The /5 was advertised as the fastest and sportiest BMW motorcycle ever. Hans-Günther von der Marwitz was entrusted with the /5’s design, and as an enthusiastic motorcyclist, he continued the tradition initiated by Rudolf Schleicher and Alexander von Falkenhausen. Used to racing an AJS 7R, von der Marwitz was dismayed at the handling of the Earles-fork /2, and when assigned to the design of the next-generation BMW motorcycle, von der Marwitz wanted it to handle as well as a Manx Norton. The engine design was all new, with three displacements offered: 498, 599, and 745cc, all sharing the same basic architecture. A number of significant design features set it apart from the earlier /2. Inside the one-piece aluminum, internally reinforced tunnel housing crankcase was a one-piece forged crankshaft (without a center bearing to minimize cylinder offset) running in plain bearings. The camshaft was situated underneath the engine, driven by a duplex chain from the front of the crankshaft, and many components came straight off the automotive production line, notably the three-layer plain bearings for the crank and con rods. As the bearings required high-pressure lubrication, an Eaton trochoidal oil pump was fitted at the rear of the camshaft, while at the front was a three-phase 180-watt alternator powering the new 12-volt electrical system. Battery and coil ignition with an automatic advance replaced the earlier magneto, and above the engine (on the R60 and R75 and optional on the R50) was an electric starter motor. Although the valve actuation system retained pushrods, as the pushrod tubes were now underneath the cylinders, the engine looked more modern. Aluminum, used extensively to minimize the effect of the heavy starting system, included alloy instead of steel-cylinder barrels, with a cast-iron sleeve bonded to the cylinder through the Al-Fin process. The European R50/5 had a lower handlebar. The seat on the early /5shad chrome passenger handles and there were no side covers. BMW Group Archives The cylinder heads were also new, with a much shallower included valve angle of 65 degrees. The R75/5 had large 42mm and 38mm valves, and a more radical camshaft than the R50/5 and R60/5. The R60/5 valves were 38mm and 34mm, with the R50/5 receiving 34mm and 32mm valves. The R75/5 also had Bing Constant Velocity carburetors rather than the Bing concentric carburetors on the smaller versions. The /5 included a completely new air intake system, with the air filter incorporated inside the engine cases, with a rear facing air intake grille. As the air intake faced rearward, there was no ram air effect, but the air filter volume was 60 percent larger than that of the R69S. A four-speed three-shaft gearbox bolted on the rear of the engine. Although the gearbox shifted more smoothly than earlier BMW twins, it still wasn’t flawless and many modifications to the shifting mechanism were made during the next few years. New was the backbone-type, double-loop frame designed exclusively for solo riding. As the frame was constructed of variable section-tapered and oval tubing with a bolted-on rear subframe, the strength was questionable, but it remained essentially unchanged until 1996. Designer von der Marwitz was convinced too much frame stiffness was detrimental for a street motorcycle, the short swingarm also impeding stability, and criticism of the handling soon saw the /5 earning the unflattering nickname “rubber cow.” Suspension included the Fichtel & Sachs leading-axle telescopic fork of the earlier US /2, providing a generous 8.2 inches of travel, with twin Boge shock absorbers at the rear. Practical features extended to a large 24-liter (6.35-gallon) fuel tank and generously sized dual seat. With a host of lightweight features, including fiberglass fenders, the new /5 series models were also reasonably light for their class. The /5 BMW moved away from the company’s decades-old tradition of primarily offering only plain black, although nearly all /5s for the United States were black in 1970 and 1971. Strangely, while the /5 represented a huge step in modernity in most respects, several archaic features remained, notably the primeval plunger ignition key and antique instrument cluster incorporated in the headlamp. The /5 certainly vindicated Bönsch’s optimism. The R75/5 was no longer a staid and stodgy motorcycle only for the initiated diehard. For a rider interested in long-distance, comfortable, high-speed travel, there was simply no other contender in 1969. Here was a motorcycle that could reliably cruise all day at 100 miles per hour, with all the conveniences expected of modern machinery. Offering respectable handling, and adequate performance, the new boxer, especially the R75/5—the first official 750cc twin since the military R75 of 1942–1944—was immediately successful. When it was released in August 1969, even the skeptics were impressed. R60/5 production commenced at Spandau in September, with the R75/5 in October and the R50/5 in November. During 1970, 12,346 examples of the /5 series were sold. Motorcycle sales hadn’t been as strong since 1955, and the future of the /5 was secure. The first US/5s appeared on the East Coast in January 1970 and the West Coast in February, and most of these were R75/5s. Only a few R50/5s were sold in the United States. Buy from an Online Retailer US: UK: Get a close look at every production motorcycle ever built by BMW. The Complete Book of BMW Motorcycles is a thorough year-by-year guide to every production machine ever built by Germany’s leading motorcycle manufacturer. All the classic bikes are here–pre-World War II BMWs such as the R5 that defined performance in that era; the military R12 that carried the Wehrmacht as it blitzkrieged its way across Europe; the Earles-forked R69S that offered the perfect platform for mounting a Steib sidecar; the R90S cafe racer; the K1 “flying brick”; and the GS (Gelände Sport) series that launched a dual-sport revolution, right up to today’s world-class S1000RR. All of BMW’s bike families are covered–the side-valve machines from the early years, the early overhead-valve performance bikes, the postwar Airheads and Oilheads, the four- and six-cylinder touring bikes, the early pushrod singles, the modern overhead-cam singles, the latest parallel twins, and inline four-cylinder sport bikes. From the first model, the R32 that launched BMW’s motorcycle dynasty, to the latest (and fastest) model, the World-Superbike-dominating S1000RR, The Complete Book of BMW Motorcycles captures nearly a century of motorcycling excellence with a combination of historic and contemporary photos. Complete technical specifications for each model make this book a must-have for any serious BMW aficionado. Don’t miss the most thorough reference to these outstanding German motorcycles available today! Share article facebook twitter google pinterest If you have any comments on this article please contact us or get in touch via social media.