🏷️ Basic Information Identification Make: BMW Model: R90 Year: 1980 Codes Model Code: R90/6 👋 Introduction Market Position Positioning: A highly regarded classic motorcycle, appealing to enthusiasts seeking reliable performance and timeless design. Competitive Analysis Competitors: Competed with other large displacement motorcycles of its era, such as Honda CB750, Kawasaki Z1, and Moto Guzzi V-twin models. Key Features Distinctive Features: Shaft drive, horizontally opposed twin-cylinder engine, comfortable touring ergonomics, robust build quality. Value Proposition Manual Value: Essential for DIY owners to maintain, repair, and restore the iconic R90, ensuring long-term reliability and preserving its value. 📋 Manual Details Coverage Areas Primary Coverage: Comprehensive service and repair procedures for the BMW R90 motorcycle. Secondary Coverage: Maintenance schedules, troubleshooting, diagnostics, electrical diagrams, specifications, and parts information. Page Count Estimated Pages: 350-450 Manual Type Type: Service and Repair Manual Language Language: English Format Format: Digital Download (likely PDF) 📖 Manual Coverage Systems Covered 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). Procedures Included 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. Technical Depth Depth: Comprehensive from basic maintenance to complete engine and transmission rebuilds, including detailed electrical troubleshooting. 📊 Manual Specifications File Format Digital Format: PDF (Portable Document Format) Searchability: Likely text-searchable if optically scanned and processed. Print Quality Digital Quality: High-resolution scans of original factory manuals, ensuring clarity of text and diagrams. Binding Type Digital Binding: N/A (digital download) Paper Type Digital Paper: N/A (digital download) ⚙️ Engine Specifications Primary Engine 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) Compression Ratio: 9.5:1 Performance Horsepower: 60 hp (45 kW) @ 6250 rpm Torque: 74 Nm (55 lb-ft) @ 5000 rpm Fuel System Carburetors: 2 x Bing 32mm constant-velocity carburetors Fuel Type: Unleaded gasoline (minimum 91 octane recommended) Lubrication Oil Type: API SG or higher, SAE 20W-50 motorcycle oil Ignition Ignition System: Battery-coil, dual ignition system (two spark plugs per cylinder) 🔧 Transmission Standard Transmission Type: 5-speed constant-mesh gearbox Clutch: Dry, single-plate, diaphragm spring clutch Final Drive: Shaft drive to rear wheel Features Gear Ratios: Refer to manual for specific gear ratios. Transmission Fluid: API GL-5, SAE 80W-90 gear oil 📐 Dimensions Exterior Length: Approx. 2220 mm (87.4 in) Width: Approx. 870 mm (34.3 in) Height: Approx. 1230 mm (48.4 in) Weights Dry Weight: Approx. 215 kg (474 lbs) Fuel Tank Capacity: 18 Liters (4.75 US gal) 🛡️ Safety Features Ratings Safety Features: Dual ignition for enhanced reliability, robust braking system for its era. Active Features Braking System: Front: Single 280 mm disc with hydraulic caliper. Rear: Drum brake. Passive Features Frame Construction: Steel tube duplex cradle frame for rigidity and stability. 💡 Technology Features Infotainment Infotainment Features: N/A (period appropriate for basic motorcycle functionality). Technical Innovations Innovations: Shaft drive provided a cleaner, lower-maintenance alternative to chain drive. Dual ignition improved combustion efficiency and reliability. 🔧 Maintenance Service Intervals 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 Fluid Specifications 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) Brake Fluid Type: DOT 4 Known Issues 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. 📚 Vehicle History Brand Heritage Heritage: BMW has a long-standing reputation for engineering excellence and producing reliable motorcycles with innovative features, dating back to the early 20th century. Model Evolution 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 Production Years: 1973-1976 (R90/6 model) Manufacturing Location: Berlin, Germany 🏆 Awards & Recognition Recognitions Historical Acclaim: Widely praised for its touring comfort, build quality, and smooth, torquey engine, establishing BMW as a premier motorcycle manufacturer.