Segment:
Classic Motorcycle / Performance Touring
Target Audience:
BMW R90 owners, enthusiasts, independent repair shops, restorers
Competitors:
Moto Guzzi California, Honda GL1000 Gold Wing (early models), Kawasaki KZ1000
Vehicle Appeal:
Shaft drive, boxer twin engine, touring capability, build quality
Value Proposition:
Provides the essential technical documentation to maintain and repair a classic BMW motorcycle, crucial for preserving its value and functionality.
Engine:
Complete engine disassembly, assembly, inspection, tuning, carburetor overhaul, ignition system diagnostics, cooling system, exhaust system
Transmission:
Gearbox removal, disassembly, assembly, inspection, maintenance, clutch service
Drivetrain:
Final drive inspection and maintenance, driveshaft service
Brakes:
Hydraulic system maintenance, brake pad/shoe replacement, caliper/master cylinder service, bleeding procedures
Suspension:
Front fork service, rear shock absorber replacement, swingarm maintenance
Electrical:
Wiring diagrams, battery service, charging system diagnostics, lighting, ignition system troubleshooting, starter motor, instrumentation
Fuel System:
Fuel tank inspection, fuel lines, fuel pump (if applicable), carburetor adjustments and rebuilding
Bodywork:
Body panel removal and installation, fairings, seat, fenders, tank mounting
Maintenance:
Routine servicing, oil changes, filter replacements, lubrication, valve adjustments, spark plug replacement, chain adjustment
Troubleshooting:
Diagnostic charts, common problem identification and solutions
Repair:
Detailed step-by-step instructions for component replacement and repair
Rebuild:
Comprehensive instructions for engine and gearbox rebuilding
Refurbishment:
Guidance on restoring components and aesthetics
Depth:
In-depth, from basic maintenance to complete engine rebuilds and electrical system diagnostics.
Engine Type:
Air-cooled, four-stroke, flat-twin (boxer)
Bore X Stroke:
90 mm x 70.6 mm
Compression Ratio:
8.2:1 (typical, may vary slightly)
Valvetrain:
OHV, 2 valves per cylinder
Power Output:
Approx. 60 hp @ 6250 rpm
Torque:
Approx. 75 Nm @ 4500 rpm
Carburetors:
2 x Bing 32mm constant velocity carburetors
Fuel Type:
Unleaded gasoline (minimum 91 octane recommended)
Oil Capacity:
Approx. 2.5 liters (including filter)
Gear Ratios:
Specific ratios detailed in manual (e.g., 1st: 3.16, 2nd: 2.04, 3rd: 1.44, 4th: 1.18, 5th: 1.00)
Clutch:
Dry, single plate
Transmission Fluid:
Gear oil (e.g., SAE 75W/90 or specific BMW recommendation)
Width:
Approx. 850 mm (over handlebars)
Height:
Approx. 1370 mm (over handlebars)
Dry Weight:
Approx. 205 kg
Gross Vehicle Weight Rating:
Not typically specified for motorcycles, but payload capacity is relevant.
Fuel Capacity:
Approx. 18 liters
Certification:
N/A (Motorcycle safety ratings differ from cars and are often manufacturer-specific for the era)
Brakes:
Dual disc front, single disc rear (or drum on some early models/variants)
Suspension:
Telescopic front forks, dual rear shock absorbers contributing to stability
Lighting:
Halogen headlamp, LED taillight/indicators (if upgraded)
Oil Change:
Every 5,000 - 10,000 km or annually
Valve Adjustment:
Every 10,000 km
Spark Plug Replacement:
Every 10,000 - 20,000 km
Final Drive Oil:
Every 20,000 km
Engine Oil:
SAE 20W-50 or SAE 10W-40 (depending on climate), API SG or higher
Brake Fluid:
DOT 3 or DOT 4 (DOT 5 silicone fluid not recommended unless specifically stated by BMW for this model)
Transmission Fluid:
SAE 75W/90 GL-5 gear oil
Common Wear Items:
Clutch wear, front fork seals, rear shock absorber degradation, starter motor brushes, camshaft wear (rare but possible), ignition coil failure.
Electrical Quirks:
Loose connections in the headlight bucket, aging wiring insulation, regulator/rectifier issues.
Carburetor Issues:
Bing carburetors can be sensitive to dirt and require precise adjustment; jet clogging.
Heritage:
BMW Motorrad, renowned for engineering, reliability, and innovation, particularly in boxer engine technology and shaft drive.
Predecessors:
BMW R75/5, R75/6, R90/6
Successors:
BMW R100 series (R100RS, R100RT, R100GS)
Production Years:
1973-1976 (R90/6 and R90S), with 1989 being an outlier for a 'full service repair manual' context, suggesting a focus on maintaining existing models.
Manufacturing Location:
Berlin, Germany
