Positioning:
A highly regarded classic motorcycle, appealing to enthusiasts seeking reliable performance and timeless design.
Competitors:
Competed with other large displacement motorcycles of its era, such as Honda CB750, Kawasaki Z1, and Moto Guzzi V-twin models.
Distinctive Features:
Shaft drive, horizontally opposed twin-cylinder engine, comfortable touring ergonomics, robust build quality.
Manual Value:
Essential for DIY owners to maintain, repair, and restore the iconic R90, ensuring long-term reliability and preserving its value.
Primary Coverage:
Comprehensive service and repair procedures for the BMW R90 motorcycle.
Secondary Coverage:
Maintenance schedules, troubleshooting, diagnostics, electrical diagrams, specifications, and parts information.
Type:
Service and Repair Manual
Format:
Digital Download (likely PDF)
Engine:
Complete overhaul, tuning, carburetion, ignition, cooling, lubrication.
Transmission:
Gearbox disassembly, assembly, clutch operation, final drive.
Electrical System:
Wiring diagrams, battery, charging system, lighting, ignition system components, starter motor.
Chassis:
Frame inspection, suspension (forks, rear shocks), steering, wheels, spokes.
Brakes:
Hydraulic system, disc brake servicing, fluid replacement, caliper maintenance.
Fuel System:
Fuel tank, fuel lines, fuel pump, carburetor adjustments (Bing).
Maintenance:
Regular servicing, oil changes, filter replacements, spark plug replacement, valve adjustments.
Troubleshooting:
Diagnostic procedures for common running problems, starting issues, electrical faults.
Repair:
Detailed step-by-step instructions for component replacement and repair.
Rebuilds:
Complete engine and gearbox rebuild procedures.
Depth:
Comprehensive from basic maintenance to complete engine and transmission rebuilds, including detailed electrical troubleshooting.
Engine Type:
Air-cooled, four-stroke, horizontally opposed boxer twin
Displacement:
897 cc (54.7 cu in)
Bore X Stroke:
90 mm x 70.6 mm (3.54 in x 2.78 in)
Horsepower:
60 hp (45 kW) @ 6250 rpm
Torque:
74 Nm (55 lb-ft) @ 5000 rpm
Carburetors:
2 x Bing 32mm constant-velocity carburetors
Fuel Type:
Unleaded gasoline (minimum 91 octane recommended)
Oil Type:
API SG or higher, SAE 20W-50 motorcycle oil
Ignition System:
Battery-coil, dual ignition system (two spark plugs per cylinder)
Transmission Type:
5-speed constant-mesh gearbox
Clutch:
Dry, single-plate, diaphragm spring clutch
Final Drive:
Shaft drive to rear wheel
Gear Ratios:
Refer to manual for specific gear ratios.
Transmission Fluid:
API GL-5, SAE 80W-90 gear oil
Oil Change:
Every 3,000 miles (5,000 km) or annually, whichever comes first.
Valve Adjustment:
Every 6,000 miles (10,000 km)
Spark Plug Replacement:
Every 6,000 miles (10,000 km) or as needed based on inspection.
Brake Fluid Flush:
Every 2 years
Engine Oil Capacity:
Approx. 2.2 Liters (2.3 US qt) with filter change.
Transmission Oil Capacity:
Approx. 1.0 Liter (1.05 US qt)
Final Drive Oil Capacity:
Approx. 0.2 Liters (0.21 US qt)
Common Issues:
Oil leaks from cylinder base gaskets, wear in the transmission output shaft seal, occasional issues with the automatic ignition advance mechanism.
Preventative Maintenance:
Regular inspection of seals and gaskets, proper engine temperature management, periodic carburetor synchronization.
Heritage:
BMW has a long-standing reputation for engineering excellence and producing reliable motorcycles with innovative features, dating back to the early 20th century.
Predecessors:
Evolved from earlier Boxer twins like the R75/5 and R60/6, featuring improvements in performance and technology.
Successors:
Paved the way for later Boxer models like the R100 series, continuing the Boxer legacy.
Production Years:
1973-1976 (R90/6 model)
Manufacturing Location:
Berlin, Germany
