BMW R75/5

The R75/5 is a BMW motorcycle, with a 750 cc boxer twin engine, that was manufactured in Berlin, Germany, by the "Bayerische Motoren Werke" (BMW Aktiengesellschaft).

History

For the 1970 model year, BMW entered the age of modern motorcycles with three new BMW models having engine capacities of 500 cc (R50/5), 600 cc (R60/5), and at the top of the line 750 cc (R75/5). The r75/5 was one of the fastest production motorcycles of the time, topping out at 109 mph (175 km/h). The "slash-5" series came out just in time to meet the rising demand for sport bikes. All so-called "slash-5" models were manufactured at BMW's factory in the Spandau suburb of Berlin, BMW having transferred all motorcycle production there from Munich in the late 1960s. BMW had stopped production in Munich of the last “Slash-2” models, with their Earles forks, kick starters, 6 volt electrical systems, underpowered brakes, and frames descended from pre-war BMWs for use with sidecars. The new, “Slash-5” series of BMWs offered a 12 volt electrical system, electric starters as well as the retained kick starter, telescopic forks, and improved brakes. The sidecar was no longer factored into the design, allowing for better handling. BMW also introduced with this model non-metallic fenders and tail light housings for the first time. The use of plastic and other non-metallic materials helped arrive at a motorcycle weighing only 463 lb (210 kg), nearly the lightest 750 cc bike of the era. These motorcycles were (and are) extremely reliable. It was (and is) not uncommon to encounter BMW "slash-5" motorcycles that have never been through a complete overhaul and have well over 100,000 miles (161,000 km). Such endurance was not common for the era.

Model year 1972 saw the introduction of the 4 US gallon (15 litre) “toaster” tank with chrome side panels, so named because of its resemblance to a kitchen toaster. For the second half of the 1973 model year, BMW lengthened the rear swingarm 2.5 inches (6.4 cm), resulting in that is known now as the “long wheel base” 1973½ “LWB” models. This improved handling and enabled a larger battery to be installed behind the engine while retaining the kick starter.

In 1974, BMW introduced the “Slash-6” models [http://jeff.dean.home.att.net/r756.htm] , which offered numerous improvements, most notably disk front brakes, more and better instrumentation, and a five-speed transmission. The fabled “toaster” tank, however, was consigned to the dust bins of history.

Technical Data

All slash-5 models have air-cooled, four-stroke, opposed-twin (boxer) engines with hemispherical combustion chambers. Their engine housings are one-piece tunnels housings. The camshaft, driven by a duplex chain, runs at half of the engine speed and is located below the crankshaft. This is the reverse arrangement from the /2 models and allows gravity to assist the delivery of oil to the camshaft. Valves are actuated by the camshaft through hardened followers, push rods, and rocker arms. The 500 cc and 600 cc models are equipped with Bing slide-type carburetors with 26 mm throats. The R75/5 comes with 32 mm Bing CV (Constant Vacuum/constant depression) type carburetors. As in all BMW motorcycles at the time, the clutch is a single-disk dry clutch. The slash-5 models have four-speed transmissions and come with kick-starters as well as electric starters. The kick starters are less sturdy than on previous models and are a frequent point of failure, most often due to incorrect kick starting technique. They were intended for emergency use in the incident of an electrical failure. When properly tuned, a slash-5 can be started by operating the kick start lever with the hand, requiring very little force to start the engine. [ http://w6rec.com/duane/bmw/trans/index.htm "/2 and /5 BMW kick starter gear information" ] Final drive is by shaft, running from the transmission by universal joint to an oil bath within the right rear swing arm and connecting to a bevel gear and ring gear on the other end. Unlike the slash-2 models, the slash-5 models are equipped with telescopic front forks, 12-volt alternator and electrics, and standard tachometer and turn signals.

References

ee also

* BMW Motorcycles
* BMW R60/2
* BMW R1200RT
* Motorcycle Forks
* Motorcycles
* Motorcycle Swingarms
* Motorcycle Suspensions
* Motorcycle Types

External links

* [http://jeff.dean.home.att.net/r75.htm "750 cc 1973 BMW “Toaster” R75/5 LWB"]
* [http://bmwdean.home.att.net/r75.htm "1973½ BMW Long Wheel Base (LWB) R75/5"]
* [http://jeff.dean.home.att.net/r75-5.html "BMW R75/5 Specifications"]
* [http://bmwdean.home.att.net/r75-serial-nos.htm R75/5 Engine Serial Numbers]
* [http://www.eecs.umich.edu/~deroo/bike.dir/owners-manual.dir/owners-manual.html Slash-5 Owner's Manual On Line]
* [http://www.5united.net/ "5 United Classic BMW Motorcycle Club"]

* [http://www.slash5.net/slash5mn.html Slash-5 Service Manual On Line]
* [http://www.slash5.net/Slash5.html Slash-5 Parts List On Line]
* [http://jeff.dean.home.att.net/r75roadtest.htm "The Wayfarer's Choice, Cycle World" R75/5 road test, July 1973]
* [http://bmwdean.home.att.net/fueltanks.htm "Fuel tanks on BMW motorcycles: 1970 - 1973"]