BMW R 69 S
With Ian Falloon
Though BMW has produced quite a lot of single, twin, 4 and six-cylinder bikes, it’s the boxer twin that has grow to be the BMW trademark. Ever for the reason that first R 32 of 1923, probably the most prized BMWs have been flat twins, and one of the crucial wanted is the 600 cc R 69 S.
Produced between 1960 and 1969 the R 69 S owed its origins to the five hundred cc R 51/3 of 1951. Whereas the R 51/3 engine structure was much like that of the sooner pre-war overhead valve twins there have been many enhancements. These included a single camshaft pushed by helical reduce gears as a substitute of the sooner twin camshaft design with its lengthy wear-prone timing chain.
Different developments noticed the magneto and generator now housed inside redesigned engine covers however retained was the pressed-up crankshaft working on curler bearings. Nevertheless, whereas the engine featured many enhancements the overall chassis was carried over from the pre-war fashions. This included a rudimentary telescopic entrance fork and doubtful plunger rear finish.
Contemplating BMW rose from the ashes on the finish of World Battle II they went from energy to energy within the early Fifties. For 1952 a 72 x 73 mm 594 cc R 67 and the next efficiency 35 horsepower R 68 joined the R 51/3. By late 1953 the 100,000th post-war bike left the rebuilt Munich works.
In 1955 the twins lastly obtained a brand new chassis, this following the bizarre type of the RS 54 racer launched a 12 months earlier. The working gear now included swingarm suspension entrance and rear, with the driveshaft included inside the rear fork leg. Whereas swingarm rear suspension was now thought of mainstream an uncommon leading-link Earles fork changed the same old telescopic entrance fork.
Whereas offering built-in anti-dive underneath exhausting braking, the Earles fork was actually extra appropriate for sidecar use, a preferred different within the Fifties. These new twins grew to become the five hundred cc R 50 and 600 cc R 69 however additionally they coincided with a normal downturn in bike gross sales that noticed many Italian and German makes disappear altogether.
BMW additionally narrowly prevented chapter till the success of the BMW 700 automobile throughout 1959. Regardless of the gloomy instances, up to date twin-cylinder bikes had been launched throughout 1960, one in every of these being the sporting R 69 S.
Ostensibly similar to the touring R 69, beneath the R 69 S’s related exterior was a reworked engine. With a 9.5:1 compression ratio and twin 26 mm Bing carburettors the ability was 42 horsepower at 7,000 rpm. A timed rotary disc engine breather was mounted on the entrance of the camshaft and a bigger air filter and new mufflers improved gasoline circulation.
Finishing the efficiency specification was a more in-depth ratio four-speed gearbox and a hydraulic, relatively than friction, steering damper. The chassis was carried over from the R 69, with 18-inch alloy rimmed wheels entrance and rear and a 200 mm twin-leading shoe entrance brake. Though the R 69 S weighed a substantial 202 kg there have been few machines obtainable at the moment that might comfortably and reliably cruise at excessive pace on the German Autobahns.
An R 69 S wasn’t as agile as a comparable British twin, and there have been some preliminary issues if the engine was revved unduly exhausting. However after BMW included a vibration damper on the top of the crankshaft from 1963 the R 69 S would run all day at its most pace of round 175 km/h.
This was one thing you couldn’t say in regards to the British competitors. BMW established an unrivalled repute for reliability when the Danny Liska rode his R60 from the Arctic Circle in northern Alaska to Tierra del Fuego on the tip of South America. The primary particular person to take action on a bike, over a interval of six months between 1960 and 1961, Liska lined 153,000 km.
The R 69 S was additionally very profitable in endurance racing; René Maucherat and René Vasseur successful the 1960 24-hour Bol d’Or at Montlhéry. After successful the Barcelona 24-hour race at Montjuich in 1959 on an R69, Peter Darvill, once more partnered with Bruce Daniels, narrowly did not win in 1960. However with manufacturing facility help for his or her R 69 S, they repeated their 1959 success in 1961.
This 12 months additionally they received the Silverstone 1000 km race. In September 1968 Kurt Liebmann and Fred Simone took the victory within the Virginia Worldwide Raceway 5-Hour race on an Amol Precision R 69 US. John Potter and William van Houten had been second on an analogous machine. The R 69 S additionally rekindled BMW’s curiosity in off-road competitors; Sebastian Nachtmann, successful a gold medal within the 1960 ISDT at Unhealthy Aussee, Austria, on his manufacturing facility R 69 S.
Sadly the R 69 S’s conservatism counted towards it through the Sixties. Solely obtainable in black with white pin striping (or white or pink to particular order) they had been at all times costly and unique. In opposition to the nice seems to be and uncooked energy of the British vertical twin the BMW was seen as an anachronism.
As an alternative of a tiny gasoline tank and slim seat the R 69 S provided a 17 or 24-litre tank, small solo saddle or massive twin seat. The one try at modernisation was the choice of recent long-travel telescopic forks for the U.S. market in 1967. Nevertheless, these weren’t well-liked and eschewed by the normal BMW purchaser in favour of the normal Earles fork model.
By 1969 the market required a brand new machine, and economics dictated that the R 69 S engine, with its built-up crankshaft and gear-driven camshaft, get replaced by another appropriate for mass manufacturing. With over 11,000 produced between 1960 and 1969 the R 69 S will not be a restricted manufacturing machine, however it’s nonetheless consultant of that earlier period when the accountants didn’t rule the engineers.
As a bike possessing all these standard BMW qualities of consolation and longevity, the R 69 S offered the most effective of each worlds. An eminently sensible and useable traditional bike, the R 69 S has justifiably earned a spot as one of the crucial fascinating post-war BMW bikes.
BMW R 69 S Specs
|BMW R 69 S Specs
|Air-cooled, four-stroke two-cylinder, horizontally-opposed Boxer, push-rod operated, two-valves per cylinder, 594 cc
|Bore x Stroke
|72 x 73 mm
|31.3 kW @ 7000 rpm
|Twin Bing carburettors
|Magneto, electrical begin
|Twin loop, metal tubular
|Telescopic fork, hydraulic damping
|200 mm Drum, entrance & rear
|3.50 x 18, 4.00 x 18
|200 kg (Moist)