The BMW R80 GS and R100 GS motorcycles, produced in 1991, represent a significant chapter in adventure touring. These robust machines, powered by air-cooled boxer twin-cylinder engines, were engineered for both on-road comfort and off-road capability, establishing BMW's reputation in this segment. With their durable tubular steel frames and innovative Monolever rear suspension, the GS models offered a unique blend of performance and reliability, making them ideal for long-distance journeys and challenging terrain. The R80 GS, with its 797.5 cc engine, and the more powerful R100 GS, featuring a 980 cc displacement, both exemplify BMW's commitment to engineering excellence and rider-focused design. This workshop manual provides comprehensive guidance for the maintenance, repair, and troubleshooting of the 1991 BMW R80 GS and R100 GS models. It covers all major systems, including detailed procedures for the engine, fuel system, ignition, transmission, drivetrain, suspension, brakes, and electrical systems. The manual includes essential information on scheduled maintenance, engine and gearbox overhauls, carburetor tuning, and electrical diagnostics, along with critical torque specifications and technical data. Its purpose is to equip owners, technicians, and mechanics with the necessary knowledge to ensure the optimal performance, longevity, and safety of these iconic motorcycles. 🏷️ Basic Information Identification Make: BMW Model: R80 GS / R100 GS Year: 1991 Product Type: Service Repair Workshop Manual 👋 Introduction Market Position Target Audience: Owners of BMW R80 GS and R100 GS motorcycles, independent repair shops, and BMW motorcycle enthusiasts. Competitive Analysis Manual Type Comparison: This is a comprehensive workshop manual, far exceeding the scope of a basic owner's manual. It provides the technical depth required for genuine servicing and repairs. Key Features Authenticity: Represents information as used by professional mechanics, providing accurate and reliable repair data. Accessibility: Digital PDF format allows for easy storage, search, and viewing on multiple devices. Comprehensiveness: Covers virtually all aspects of maintenance, troubleshooting, and repair for the specified models. 📋 Manual Details Coverage Areas Primary Coverage: BMW R80 GS and R100 GS Models Specific Models Covered: R80GS, R100GS Model Year Coverage: 1991 Page Count Estimated Pages: Over 300 pages (typical for comprehensive manuals of this era and type) Manual Type Type: Workshop Manual / Service Manual / Repair Manual Language Language: English Format Format: PDF Download 📖 Manual Coverage Systems Covered Engine: Detailed inspection, disassembly, assembly, tuning, and repair procedures for the BMW boxer twin engines. Fuel System: Carburetor (Bing 32/40/35/40) overhaul, adjustment, troubleshooting, fuel pump, fuel lines, and fuel tank maintenance. Ignition System: Ignition timing, spark plugs, ignition coils, control unit troubleshooting and replacement. Transmission: Gearbox (5-speed) disassembly, assembly, clutch service, troubleshooting, and lubrication. Drivetrain: Final drive, driveshaft, universal joints, and rear wheel hub maintenance and repair. Suspension: Front forks (includingモノショック (Monolever) system), rear shock absorber, and swingarm maintenance, adjustments, and seal replacement. Brakes: Front and rear brake systems (disc brakes), master cylinders, brake calipers, brake lines, and fluid replacement. Electrical System: Wiring diagrams, battery maintenance, starter motor, alternator, lighting system, horn, and instrument cluster troubleshooting. Frame And Bodywork: Frame inspection, fairing removal/installation, seat, fuel tank, fenders, and luggage rack maintenance. Wheels And Tires: Spoke wheel maintenance, bearing replacement, tire mounting, and balancing. Procedures Included Scheduled Maintenance: Oil changes, filter replacements, spark plug checks, valve clearance adjustments, brake fluid flush, and general inspection schedules. Troubleshooting: Diagnostic flowcharts and symptom-based troubleshooting for common mechanical and electrical issues. Engine Rebuild: Complete procedures for engine disassembly, component inspection, machining recommendations, and reassembly. Transmission Overhaul: Step-by-step guide for gearbox disassembly, gear inspection, bearing replacement, and reassembly. Carburetor Tuning: Detailed instructions for synchronizing and adjusting Bing carburetors for optimal performance. Electrical Diagnosis: Guidance on testing electrical components, diagnosing shorts, open circuits, and charging system faults. Suspension Adjustments: Instructions for adjusting preload and damping on front and rear suspension units. Brake System Service: Procedures for bleeding brakes, replacing pads, and overhauling master cylinders and calipers. Technical Depth Depth: Comprehensive, covering basic maintenance to full engine and gearbox rebuilds, suitable for professional mechanics and experienced DIY enthusiasts. Diagnostic Level: Advanced diagnostic procedures and troubleshooting guides. Specifications Detail: Includes detailed torque specifications, clearances, and critical measurements for all components. 📊 Manual Specifications File Format Format: PDF (Portable Document Format) Searchability: Likely text-searchable if digitally rendered from an original manual with OCR, allowing quick access to information. Print Quality Quality: Dependent on the source scan. Professional scans aim for clear text and legible diagrams. Optimized for digital viewing and printing. Binding Type Binding: N/A (Digital PDF format) Paper Type Paper Type: N/A (Digital PDF format) ⚙️ Engine Specifications Primary Engine Engine Type: Air-cooled, four-stroke, horizontally opposed boxer twin-cylinder Bore X Stroke R80: 80.0 mm x 78.0 mm (R80GS) Bore X Stroke R100: 94.0 mm x 70.7 mm (R100GS) Displacement R80: 797.5 cc (R80GS) Displacement R100: 980 cc (R100GS) Compression Ratio R80: 8.2:1 (R80GS) Compression Ratio R100: 8.5:1 (R100GS) Performance Horsepower R80: Approx. 50 HP @...