1941–1946 BMW R75 Service Manual (P/N 01 99 9 099 421)

• Original OEM factory publication, form number 01 99 9 099 421
• Covers 1973–1976 BMW R 60/6, R 75/6, R 90/6, and R 90 S motorcycles
• 50 pages of technical data detailing engine overhaul procedures, wiring system diagnostics, and fuel supply maintenance
• Definitive factory reference for servicing the /6 boxer engine series, incorporating all crucial performance data and tightening specifications

Engine and Fuel System Documentation

Tackling a classic /6 boxer engine requires precise factory data. This manual outlines the exact technical parameters for engine removal, cylinder head servicing, and crankcase internals. You will find detailed tolerance charts covering piston and ring clearances, crankshaft bearing stages, and valve timing. The fuel system sections detail tuning specifications for the Bing constant depression carburetors on the R 75/6, as well as the Dellorto units equipped on the R 90 S. It also covers float level verification and air filter maintenance. When handling fuel delivery components, ensure your workspace is thoroughly ventilated and battery grounds are disconnected to prevent accidental ignition.

Specification Highlights and Electrical Data

Electrical diagnostics are straightforward with documented starter motor testing procedures, alternator output charts, and contact breaker timing metrics. Crucial tightening torque values are provided for all main engine fasteners. Cylinder head stud torque is mapped out in a specific three-stage sequence from 3.5 to 3.9 mkp (25.3–28.2 ft/lb). The main bearing journal radial clearance is strictly specified at 0.035–0.065 mm (0.0013–0.0025 inches), while the starter motor short circuit current is listed at 290 amps. Relying on these authoritative factory specifications ensures professional maintenance and engine restoration for any classic boxer build.