Positioning:
The BMW R90 series represented BMW's commitment to robust, air-cooled boxer twin motorcycles, offering a blend of touring capability and sporting performance in the early 1980s.
Competitors:
Competed with other large displacement European and Japanese motorcycles of the era, emphasizing shaft drive reliability and boxer engine characteristics.
Vehicle Highlights:
Shaft drive, opposed-twin boxer engine, robust construction, touring comfort, distinctive BMW styling.
Value:
Empowers owners to maintain and repair their classic BMW R90, ensuring longevity, preserving value, and enabling self-sufficiency in repairs.
Engine:
Detailed disassembly, assembly, tuning, troubleshooting, lubrication, cooling system, fuel system (carburetors), ignition system, exhaust system.
Transmission:
Clutch assembly, gearbox operation, maintenance, repair, final drive, driveshaft.
Chassis And Frame:
Frame inspection, fork assembly, rear suspension, steering head, wheel bearings.
Brakes:
Front and rear brake systems (drum and/or disc depending on specific R90 variant), brake fluid, bleeding procedures, component overhaul.
Electrical System:
Battery, charging system (alternator/generator), starter motor, lighting circuits, horn, ignition switch, wiring diagrams, component testing.
Fuel System:
Fuel tank, fuel lines, petcock, carburetor model specifics (e.g., Bing), tuning and synchronization.
Bodywork And Trim:
Fairing, tank cover, seat, fenders, minor bodywork repairs.
Scheduled Maintenance:
Oil changes, filter replacements, spark plug service, valve clearance adjustment, chain adjustment, lubrication points.
Troubleshooting:
Step-by-step diagnostic procedures for common and uncommon issues across all major systems.
Component Overhaul:
Complete rebuild instructions for engine, gearbox, carburetors, brakes, and electrical components.
Torque Specifications:
Essential torque values for critical fasteners across the motorcycle.
Special Tools:
Identification and usage of specialized BMW tools required for certain procedures.
Depth:
Comprehensive from basic rider maintenance to complete engine rebuilds and advanced electrical diagnostics. Suitable for home mechanics and professional technicians.
Digital Quality:
High-resolution scans, searchable text (OCR'd where applicable), printable pages.
Print Usability:
Optimized for printing, with clear diagrams and legible text.
Binding:
Not applicable (Digital Download)
Paper Quality:
Not applicable (Digital Download)
Engine Type:
Air-cooled, four-stroke, horizontally opposed twin-cylinder boxer engine.
Displacement:
897 cc (for R90/6 and R90S variants)
Bore X Stroke:
90 mm x 70.6 mm
Compression Ratio:
8.2:1 or 9.5:1 (depending on R90 variant and fuel octane requirements)
Horsepower:
Approx. 60-65 hp at 6500 rpm (R90/6); R90S higher output
Torque:
Approx. 75 Nm (R90/6)
Carburetors:
Twin Bing constant-velocity carburetors (e.g., 32mm or 40mm depending on model variant)
Ignition Type:
Contact breaker points ignition system, dual ignition coils.
Oil System:
Wet sump lubrication, driven by engine oil pump.
Type:
5-speed constant mesh gearbox
Type:
Not applicable (standard 5-speed)
Drive System:
Shaft drive to rear wheel via enclosed driveshaft.
Clutch:
Single dry plate clutch, operated by cable.
Wheelbase:
Approximately 1465 mm (57.7 inches)
Length:
Approximately 2180 mm (85.8 inches)
Dry Weight:
Approximately 210-220 kg (463-485 lbs) depending on model and equipment.
Fuel Capacity:
Approximately 24 liters (6.3 US gallons), including reserve.
Certification:
Not applicable for motorcycle safety ratings in the modern sense; adherence to manufacturing standards of the era.
Braking System:
Dual leading shoe drum brake (front) and leading/trailing shoe drum brake (rear) for R90/6, potentially disc brakes on later or specific models/options. R90S typically had front disc brake.
Frame Construction:
Steel tube frame, known for stability and durability.
Oil Change Interval:
Typically every 5,000 km (3,000 miles) or annually, whichever comes first.
Valve Adjustment Interval:
Every 10,000 km (6,000 miles) or as needed based on noise.
Spark Plug Replacement:
Every 10,000 km (6,000 miles) or as needed. Check condition and gap at 5,000 km.
Engine Oil Type:
SAE 20W-50 or SAE 10W-40 motorcycle specific, API SG or higher, or a dedicated BMW airhead oil.
Engine Oil Capacity:
Approx. 2.7 liters (2.8 US quarts) with filter change.
Gearbox Oil Type:
SAE 80W-90 hypoid gear oil.
Final Drive Oil Type:
SAE 80W-90 hypoid gear oil.
Brake Fluid Type:
DOT 3 or DOT 4 (check specific caliper requirements).
Common Problems:
Oil leaks (especially around cylinder base gaskets and output shafts), carburetor synchronization drift, wear in the steering head bearings, aging electrical components, potential for clutch wear over time.
Ignition System Notes:
Points and condenser require periodic checking and replacement for optimal performance.
Carburator Tuning:
Regular cleaning and synchronization of Bing carburetors is crucial for smooth running.
Heritage:
BMW Motorrad has a long history of producing reliable, high-quality motorcycles, particularly known for their boxer engine configurations and shaft drive systems.
Predecessors:
Successor to models like the R75/7, building on the '/7' generation platform. The R90S was a sportier variant introduced earlier, with the R90/6 being a more touring-oriented machine.
Production Period:
The R90 series, including the R90/6 and R90S, was produced roughly from 1973 (R90S) to 1976/1977, with the R90/6 being a key model in the late 70s/early 80s before the K-series. The '1982' in the product name likely refers to the applicability of this manual to models that might still be in service or used in that year, or it could be a slightly misstated year for the core model range itself, as the R90 series production largely ended before 1982, being replaced by the R100 series. The manual is likely designed for the entire lifespan of the R90 models.
Industry Standing:
The R90 series is widely regarded as a classic motorcycle, praised for its build quality, durability, and enduring appeal among enthusiasts. The R90S, in particular, was considered a benchmark sport-touring machine.
Reliability:
Generally considered very reliable and durable when properly maintained, a hallmark of BMW engineering.
