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BMW R-series motorcycle and retrofit

Rétrofit moto et BMW

Ride Mercury chose to start its motorcycle retrofit activity on the basis of BMW R Series motorcycles from the 70s to the 90s. Its two founding members are perfectly familiar with these models which they had the opportunity to prepare as part of their Mototherapy workshop for more than 10 years, only to maintain. The R series is actually the first series of BMW motorcycles. At the time, the first models were powered by single-cylinder engines (until 1966) then by twin-cylinder boxer engines to this day. The letter “R” stands for RAD (wheel in German), which allowed them to be distinguished from aircraft engines formerly manufactured by the German firm.

Style and timelessness for the BMW R series with electric conversion

The choice of BMW R Series models from the 70s to 90s for a motorcycle retrofit can be explained by several points, the first of which may be “German mechanical pragmatism”. The design structure of the BMW R series from the 5 series (1969-1973) offers a simple mechanical architecture which provides easy access to all mechanical parts and therefore, as part of a motorcycle retrofit, the easy removal of the engine block. Added to this simplicity of design is a very structured, almost “square” design where the BMW R Series engine does not “overflow” in any way onto the other elements and fits perfectly into a tubular frame. The engine impresses with the simplicity of its design with its simple, smooth central body and its characteristic two flat cylinders. The sober line and the very simplicity of the engine design have allowed Ride Mercury to design an electric “motor” which generally takes up the proportions of the original thermal engine and preserves the general line of the iconic BMW R Series from the 70s to the 90s.

Eligible BMW R series models for electric conversion (non-exhaustive list)

Ride Mercury offers its customers two options for carrying out a motorcycle retrofit on a BMW R Series base. You have an eligible motorcycle, it’s perfect! The workshop will carry out checks to validate that your model is in good condition for an electric conversion, otherwise, if possible, Ride Mercury will quote you the repair. If you do not have your own BMW R Series motorcycle for the retrofit, the workshop will find you the rare gem. Check out some of the eligible motorcycles at Ride Mercury.

BMW R 5 Series (1969-1973)

Designed by Ferdinand Jardin and Alex Von Falkenhausen, the BMW R 5 Series is the first BMW built in the new West Berlin factory. Contemporary with the Honda CB750, this model is a major turning point in the history of the German manufacturer. The Series 5 (Type 246) is available in several displacements, 498 cm3 (R50/5 – 32 hp), 599 cm3 (R60/5 -40 hp) and 745 cm3 (R750/5 – 5o hp). For the three motorcycles, the manufacturer adopted a stroke of 70.6 mm which will now be the standard on all classic BMWs (1969-1993). Beyond the shape of the combustion chamber and the profile of the cams, the size of the bore will determine the displacement of each model but also the number of cooling fins. A major development is that the 5 Series will abandon the “unreliable” cast iron cylinders of the old generation for lined aluminum elements. The most visible change remains the use of a telescopic fork from the German off-road motorcycle manufacturer Maico. BMW is thus abandoning the Earles pendulum element of the old generation. On the structure side, we find a new frame inspired by the reference in the field of the time: The Norton Featherbed. It will undergo modifications in 1973 with the grafting of a swinging arm 50 mm longer to increase ground clearance on the one hand and straight-line stability on the other hand while making it possible to accommodate a larger battery.

Ride Mercury initially favors the motorcycle retrofit of the BMW R 6 and 7-Series

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​BMW R 6 Series (1974-1976)

The BMW 6 Series is modernized and abandons the vintage headlight nacelle for an automobile-style meter unit. Improvements are made to the electrical circuit, among other things, with a more powerful alternator (280 watts) associated with a larger capacity battery. Two new large displacement cars expand the range: the statutory R 90/6 and the sporty R 90S. These new models led to the disappearance in 1977 of the BMW R75, which had become obsolete. In major changes, the BMW 6 series receive a standard 260 mm single-piston front disc brake (except the R60/6) as well as a 5-speed gearbox. Reliability of the electrical system and larger battery make the kickstarter disappear, which is now useless. The new equipment makes the 6 series heavier than a series. As for the gearbox, it retains the same timing for all versions. However, the diaphragm clutch sees its hardness increase with the displacement.

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​BMW R 7 Series (1977-1985) & BMW Monolever (1980-1994)

The 7 series saw the appearance of the first fully fairing BMWs (BMW R100 RS & R 100 RT) and versions equipped with the fork head of the R90 S, among others on the R100 S. The year 1980 saw the birth of a future bestseller with the BMW R 80 G/S for “gelände/straße“ or “off-road/road“. The first large-capacity trail bike, it is as comfortable off-road as on highway sections. Majorly, BMW adopts a single-sided swing arm with a single shock absorber placed on the right, known as Monolever, which eliminates the characteristic problem of cardan transmission: the overturning torque (the oscillation of the motorcycle from right to left). During the same period, the BMW R 80ST (1982-1984) arrived powered by an 800 cm3 air-cooled flat twin (84.8 mm bore) producing 50 hp!

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Electric conversion kit for BMW R-series


​Whether you own a BMW R 5 Series motorcycle from the 1970s or a 7 Series from the 1980s, Ride Mercury will preserve its authenticity while giving it a new lease of life. Combining style and innovative electric conversion technology is the workshop’s promise. The Ride Mercury motorcycle retrofit is part of both a civic and innovative approach and reconciles the passion for iconic motorcycles and current environmental issues.

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