This is from the site Bring a Trailer (https://bringatrailer.com/) ...
This 1951 Ardie B-251 is an uncommonly seen two-seater runabout manufactured in Nuremburg during Germany’s post-WWII recovery period. An older refurbishment was reportedly carried out by an American expat in Germany, from whom the seller purchased it while stationed there. The motorcycle was then shipped to the US in 2010, where it has been stored under cover in a garage for the ensuing six years. The engine starts and runs but will need some attention as detailed below. Documentation includes parts invoices and the original owner’s purchase paperwork from Ardie-Werk A.G., and an Ohio title is included.
Black paint still shines well overall but exhibits signs of wear including a handful of chips and a one-inch scratch on the fuel tank, and would likely benefit from a good polish. Pagusa seats, grips, fork bellows and other rubber items appear to be in good shape. A period rack and rearview mirror have been fitted, and chrome spoked wheels wear Metzlers with substantial tread remaining.
Chrome is presentable but shows light pitting throughout, and the normally chrome headlight bezel has been painted black. Age-related patina is visible on badging, fork braces and other aluminum parts. The painted steel double-cradle frame appears largely devoid of corrosion in photos.
Power comes from a 245cc two-stroke single which was last started and run in 2015 – starting is via a kick pedal and the motor runs on a 1:25 oil to fuel mixture. The carburetor will need to be cleaned, a tuneup performed and the battery replaced according to the seller. Peak power came at 5000 rpm and at just under 300 pounds, the B251 was supposedly capable of nearly 60mph when in good tune.
A four-speed manual gearbox is mounted inside the ribbed engine case and sends approximately 10.5 horsepower to the chain-driven rear wheel. Drum brakes are fitted at both ends and suspension is via a standard telescoping fork in front and Jurisch-type plunger in the rear. The bike’s last service was in Germany when it was still being used regularly.
After six years of storage the bike is being sold to help with a move to New Mexico for medical school. A handful of German service records are included in the sale, along with period technical manuals and the bike’s original German title.