Market Position:
The BMW R90 series, including the R90/6, was positioned as a premium sport-touring motorcycle in the late 1970s, known for its robust engineering, comfortable ride, and reliable boxer twin engine.
Competitors:
Competed with other European and Japanese large-displacement motorcycles of the era, such as Moto Guzzi, Laverda, and select Japanese inline-fours.
Key Features:
Shaft drive, air-cooled boxer twin, smooth power delivery, comfortable ergonomics, robust build quality, and excellent handling for its time.
Coverage:
Complete service, repair, and maintenance
Page Count:
Estimated 400-600 pages (typical for a comprehensive service manual of this era)
Manual Type:
Factory Service Manual / Workshop Manual
Format:
Downloadable Digital Format (PDF assumed)
Engine:
R90/6 Boxer Twin, engine disassembly, assembly, tuning, lubrication, cooling system
Fuel System:
Carburetor service (likely Bing 32/36mm), fuel pump, fuel lines, fuel tank
Transmission:
5-speed gearbox, clutch service, final drive
Electrical System:
Ignition system (points, coils, spark plugs), charging system (alternator, regulator), lighting, starter motor, battery
Chassis And Suspension:
Front fork (BMW Telelever variant for this era), rear shock absorbers (likely dual shocks), wheel bearings, steering head bearings
Brakes:
Front disc brake system (single caliper), rear drum brake, brake fluid specifications and bleeding procedures
Bodywork:
Frame, body panels, seat, fuel tank, fenders, minor body repairs
Preventative Maintenance:
Scheduled maintenance, oil changes, filter replacements, lubrication points, valve adjustments
Troubleshooting:
Diagnostic procedures for common issues, symptom-based troubleshooting guides
Repair And Rebuild:
Detailed step-by-step instructions for component removal, overhaul, and reassembly
Tuning And Adjustment:
Carburetor synchronization and jetting, ignition timing, idle speed adjustment
Depth:
Comprehensive: Covers everything from basic fluid changes to complete engine and transmission overhauls, including electrical system diagnostics and chassis component replacement.
Engine Type:
Air-cooled, four-stroke, horizontally opposed twin-cylinder (Boxer)
Displacement:
897.2 cc (54.7 cu in)
Bore X Stroke:
90 mm x 70.6 mm
Horsepower:
60 hp (45 kW) @ 6500 rpm
Torque:
73 Nm (54 lb-ft) @ 5000 rpm
Carburetors:
2 x Bing 32/32mm constant-velocity carburetors
Fuel Type:
Unleaded gasoline (minimum 91 octane recommended)
Transmission Type:
5-speed constant mesh gearbox
Clutch Type:
Dry, single-plate, diaphragm spring
Gear Ratios:
Typically: 1st: 2.44, 2nd: 1.72, 3rd: 1.32, 4th: 1.12, 5th: 0.96 (Subject to specific manual verification)
Safety Ratings:
N/A (Motorcycle safety standards were less formalized than automotive; focus is on mechanical integrity and rider control.)
Braking System:
Front: Hydraulic disc brake, Rear: Mechanical drum brake.
Suspension Stability:
BMW's renowned chassis and suspension tuning contributed to stable handling.
Frame Construction:
Steel tube frame providing structural integrity.
Infotainment System:
N/A (Analog instrumentation: speedometer, tachometer, odometer, basic warning lights)
Driver Assistance Features:
N/A (Rider control and mechanical systems only)
Oil Change Interval:
Every 5,000 km (3,000 miles) or annually, whichever comes first.
Valve Adjustment Interval:
Every 10,000 km (6,000 miles)
Spark Plug Replacement:
Every 10,000 km (6,000 miles)
Engine Oil Type:
API SF or SG classification, SAE 20W-40 or 20W-50 (check manual for exact recommendation)
Engine Oil Capacity:
3.0 liters (3.2 US quarts) with filter change
Transmission Oil Type:
API GL-5, SAE 80W-90 gear oil
Transmission Oil Capacity:
0.25 liters (0.26 US quarts)
Final Drive Oil Type:
API GL-5, SAE 80W-90 gear oil
Final Drive Oil Capacity:
0.16 liters (0.17 US quarts)
Brake Fluid Type:
DOT 3 or DOT 4 (check manual for specific requirement)
Common Issues:
Oil leaks (especially from cylinder head gaskets and oil pan), worn valve guides, clutch wear, electrical connections degradation, starter clutch wear.
Typical Repairs:
Valve guide replacement, piston ring replacement, carburetor overhaul, transmission seal replacement.
Brand Heritage:
BMW Motorrad, established in 1916, has a long history of producing innovative and high-quality motorcycles, particularly known for its boxer engines and shaft drive systems.
Model Lineage:
The R90 series (R90/6 and R90S) was a significant evolution of BMW's touring and sport-touring motorcycles, introducing more power and refinement over earlier models.
Production Years:
1973-1976 (R90/6 and R90S)
Manufacturing Location:
Berlin, Germany
