Sidecar

Looks like a BMW R12 or even a Zundapp KS750 by the looks of the cylinder…

ca. 1938, England — Motor engineer Mr. H. Jenneret and a passenger try out his new motorcycle and ‘oscillant’ sidecar where the driver and sidecar wheel bend at the same time. This invention stops the sidecar from turning over. — Image by © Hulton-Deutsch Collection/Corbis