This is from the site Bring a Trailer (https://bringatrailer.com/) ...
This 1978 BMW R100RS is finished in Magenta Red and is powered by an air-cooled 980cc boxer twin paired with a 5-speed transmission and shaft drive. The seller acquired the bike eight years ago from a prior owner in Texas who had stored it for many years. The seller has added about 6k miles over his ownership, during which the top and bottom ends have been rebuilt. A Dyna III electronic ignition conversion and a Reynolds ride-off center stand are fitted, and the bike was displayed at the Quail Motorcycle Gathering in 2015. Now in California, this R100RS is offered with a factory manual, tool roll, removable Krauser panniers, and a clean Arizona title in the seller’s name.
The bike is shown above at the 2015 Quail motorcycle gathering. The R100RS was the first motorcycle offered with an integral full fairing, and the bodywork is finished in Magenta Red with black lower panels on the fairing. The seller notes that the fairing and front fender were repainted with Glasurit paint from Holt BMW to correct for imperfections.
The snowflake-style aluminum wheels measure 19″ at the front and 18″ at the rear, and braking is handled by twin front and a single rear disc. A tinted factory-style Clearview screen is installed, and a Reynolds ride-off center stand is fitted. The removable Krauser panniers mount to a set of chrome tubular mounts. The seller notes that the bike retains a factory seat.
Instrumentation includes a 140-mph speedometer, a 9k-rpm tachometer, and a selection of warning lights in the primary cluster. A clock and voltage gauge housed in the inner fairing. The seller has disconnected the clock from power to remove the drain on the battery. 34k miles are shown on the mechanical odometer, approximately 6k of which were added by the seller.
The air-cooled boxer twin displaces 980cc and is fitted with a Dyna III electronic ignition conversion. Factory-rated output was 70 horsepower thanks to European-specification 40mm carburetors and exhaust, which is sent to the rear wheel via a 5-speed transmission and shaft drive. A top-end rebuild was performed shortly after the seller acquired the bike in 2013, including new Siebenrock cylinders and pistons, with heads done by Bob’s Motorwerks in Montana. The diode board, coil, and clutch were also replaced at that time.
The engine was rebuilt again approximately 2,000 miles ago in 2015 after evidence of bearing failure was found, and a new crank and bearings were fitted. The seller notes that records are available from his eight years of ownership, and the last service was a carburetor float adjustment and fuel petcock cleaning in February 2017.
The tool roll is shown above, and the factory owner’s manual is shown in the gallery. A start-up and walkaround video is viewable below.