Segment:
Classic Air-Cooled Boxer Twin Motorcycle
Competitors 1983:
Honda CB series, Kawasaki KZ series, Yamaha XS series, Moto Guzzi V-twin models
Vehicle Attributes:
Iconic air-cooled boxer twin engine, shaft drive, touring capability, robust build quality
Manual Value:
Enables owners to maintain, repair, and restore their valuable classic BMW motorcycle.
Engine:
Full engine overhaul, carburetor tuning, ignition system, lubrication system, cooling system (air-cooled), exhaust system
Transmission:
Gearbox disassembly and assembly, clutch service, final drive (shaft drive)
Chassis:
Frame inspection and repair, suspension (front forks, rear shock absorbers), steering system, wheels and tires
Brakes:
Brake system overhaul (front and rear), hydraulic components, brake pad/shoe replacement
Electrical:
Wiring diagrams, lighting system, battery, charging system, starter motor, instrumentation
Routine Maintenance:
Oil changes, filter replacements, chain adjustment (if applicable), spark plug service, general inspection
Diagnostic Troubleshooting:
Fault finding procedures, symptom analysis, common problem solutions
Rebuild Refurbishment:
Complete engine rebuild, gearbox rebuilding, suspension component replacement, electrical system repair
Special Tools:
Identification and use of specialized BMW tools required for specific tasks
Depth:
Comprehensive, from basic maintenance to complete engine and transmission rebuilds, including electrical diagnostics and bodywork.
Type:
Air-cooled, four-stroke, horizontally opposed twin-cylinder (Boxer)
Displacement:
900 cc (Approximately)
Bore X Stroke:
83 mm x 84 mm (Approximate, varies by specific R90 variant)
Compression Ratio:
9.5:1 (Typical for R90/S, may vary for R90/6)
Horsepower:
60-70 hp @ 6500-7000 rpm (Varies by R90 model)
Torque:
70-75 Nm @ 5500 rpm (Varies by R90 model)
Carburetors:
Dual Dell'Orto PHM 38 or Bing 32/40 carburetors (depending on model variant)
Fuel Type:
Unleaded Gasoline (Octane rating typically 91-95 RON)
Oil Capacity:
Approx. 2.5 - 3.0 liters
Oil Type:
SAE 20W-50 or SAE 15W-50 Motorcycle Specific (Check manual for exact recommendation)
Type:
Battery-coil ignition with breaker points or electronic ignition (depending on specific model/year).
Wheelbase:
Approx. 1465 mm (57.7 inches)
Length:
Approx. 2180 mm (85.8 inches)
Dry Weight:
Approx. 195-205 kg (430-450 lbs) depending on model variant
Gross Vehicle Weight Rating:
Approx. 390-400 kg (860-880 lbs)
Crash Safety:
N/A (Motorcycle safety standards apply, focus on rider protection and vehicle stability)
Braking System:
Front: Disc brake; Rear: Disc or Drum brake (depending on model variant).
Lighting:
Headlight, taillight, brake light, turn signals.
Oil Change Interval:
Every 3,000-5,000 km (or annually), whichever comes first.
Valve Adjustment Interval:
Every 6,000-10,000 km (check manual for exact interval and procedure).
Spark Plug Replacement:
Every 6,000-12,000 km (depending on plug type and wear).
Final Drive Oil Change:
Every 10,000-15,000 km (check manual for specific interval).
Engine Oil Viscosity:
SAE 20W-50 or SAE 15W-50 (Motorcycle specific)
Brake Fluid Type:
DOT 3 or DOT 4 (Depending on original specification, check manual for exact type and change interval).
Gearbox Oil Grade:
SAE 90 Hypoid Gear Oil
Common Wear Items:
Carburetor diaphragms, clutch plates, swingarm bearings, fork seals, ignition points (if applicable).
Electrical Quirks:
Age-related wiring degradation, regulator/rectifier issues (especially on older models).
Maintenance Documentation
Importance Of Manual:
Crucial for maintaining the longevity and performance of a classic motorcycle like the R90.
Heritage:
BMW Motorrad has a long history of producing high-quality, technologically advanced motorcycles since the early 20th century.
R Series Evolution:
The R90 series (R90/6 and R90S) represented a significant advancement in BMW's boxer-twin lineup, offering increased power and refinement over previous models.
R90S Distinction:
The R90S was the flagship model, known for its sportier styling, dual front discs, and optional fairing, setting performance benchmarks for its era.
Production Years:
1973-1976 (R90/6 and R90S models were predecessors to models leading up to 1983, R90 designation itself ended earlier)
Manufacturing Location:
Berlin, Germany (BMW Motorrad Plant)
Historical Acclaim:
The R90S, in particular, was highly acclaimed for its performance, handling, and build quality in its era.
Consumer Reviews:
Consistently praised for its reliability, touring comfort, and the unique character of its boxer engine.
Industry Standards:
Built to rigorous BMW engineering standards of the period.
