1973-1976 BMW R90, R90S, R 90/6 Service Manual (P/N 11 00 999 421)

• Original OEM publication 11 00 999 421 covering 1973–1976 BMW R60/6, R75/6, R90/6, and R90S models
• Contains 80+ pages of detailed technical diagrams, torque tables, component exploded views, and fault-finding charts
• Serves as the standard reference for R-series Boxer engines, capturing factory-specified tolerances and assembly patterns for the production run

Engine and Component Documentation

The 1973–1976 BMW service manual maps out the essential technical data for the Boxer engine lineup. It dives deep into engine internal clearances, crankshaft and connecting rod bearing tolerances, cylinder boring and honing specifications, and oil pump design parameters. For the electrical system, the documentation outlines Bosch starter and alternator testing procedures. You will also find exact contact breaker point settings and ignition timing charts.

Fuel delivery covers both Bing and Dellorto carburetor configurations, offering precise jet sizing and float level adjustments. Moving to the drivetrain, the gearbox specifications detail internal ratios and shim-adjusted axial float settings for the 5-speed transmission.

Technical Data Highlights

Engine lubrication pressure warning lamps trigger at 0.2–0.5 atmg. Cylinder head bolt torque for the R90 series requires a specific three-stage sequence, which is clearly documented in the factory charts. Intake valve clearance is set at 0.15 mm. The top compression ring gap for R90 models is specified at 0.30–0.45 mm, and the R90S fuel tank holds exactly 24 liters, including the reserve.

Working on classic airheads requires precision and an understanding of aging metallurgy. Always verify these reference figures against the complete factory documentation and ensure your workshop meets standard safety protocols before tearing down the block.