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 , 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.
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. 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.
|R 50/5||R 60/5||R 75/5|
|Bore||67 mm||73.5 mm||82 mm|
|Displacement||498 cc||599 cc||749 cc|
|Top Speed||87 mph (140 km/h)||99 mph (159 km/h)||109 mph (175 km/h)|
|Curb Weight||452 lb (205 kg)||463 lb (210 kg)||463 lb (210 kg)|
|Gross Weight Rating||881 lb (400 kg)|
|Alternator||Bosch 12 V • 180 Watts|
|Spark Plugs||Bosch W230T30 / Champion N7Y|
|Fuel Tank||4.7 or 6.3 US gallons (18 or 24 litres)|
|Tires||3.25x19 front • 4.00x18 rear|
|Rims||1.85x19 front • 1.85x18 rear|