This manual covers the BMW R51, R61, R66, and R71 models, produced between 1938 and 1941. These motorcycles represent a significant era in BMW's engineering legacy, known for their robust construction, reliable flat-twin boxer engines, and shaft drive systems. The R71, in particular, saw notable military application. These machines were designed for durability and performance, competing effectively with other European manufacturers of the time and solidifying BMW's reputation for quality.

This factory service repair manual provides comprehensive coverage for all major systems, including the engine (M51, M66, M71), transmission, drivetrain, chassis, and electrical system. It details routine maintenance procedures, step-by-step repair instructions, and troubleshooting guides for common issues. With factory-level detail, including torque specifications and diagnostic procedures, this manual is an essential resource for owners, mechanics, and technicians aiming to maintain, repair, and preserve these classic BMW motorcycles.