This is from the site Bring a Trailer (https://bringatrailer.com/) ...
This 1981 BMW R100RT is finished in Lava Red and powered by a 980cc boxer twin paired with a five-speed manual gearbox. The bike has been fitted with a brat-style seat, Renthal handlebars, a shortened front fender, and aftermarket mufflers, and also comes with a stock front fender and fairings, seat and pan, rear fender, luggage rack, and mufflers. Service since the seller’s acquisition in mid-2018 included replacement of the gearbox input shaft and several seals as well as a valve adjustment and fluid changes. This R100RT is offered at no reserve with a clean South Carolina title in the seller’s name.
The fuel tank and side covers are finished in Lava Red (508), as are the detached fairings, seat pan, and front fender. An aftermarket two-up brat-style seat, Renthal handlebar, and grips have replaced the stock items, which are also included in the sale. The seller notes scratches on the bodywork and areas of corrosion on the frame.
Black snowflake-pattern wheels wear 3.25-19 front and 4.00-18 rear Michelin Pilot Active tires which the seller notes are due for replacement. Stopping power is from dual Brembo disc brakes up front and a single version in the rear.
The air-cooled 980cc boxer twin was rated at 70 horsepower when new and drives the rear wheel via a five-speed manual gearbox and an enclosed driveshaft. The gearbox input shaft is said to have been replaced by a specialist under current ownership, while the seller fitted new cylinder head O-rings, pushrod tube gaskets, and valve cover gaskets. A valve adjustment was also performed in addition to oil changes for the engine and gearbox.
A stock seat, fenders, fairings, luggage, rack, mufflers, and handlebars will come with the bike along with the removed instrument cluster, which includes a five-digit odometer showing 18k miles. Total mileage is unknown. A cold start and riding video can be viewed below.