Segment:
Dual-sport / Adventure motorcycle
Target Audience:
Owners of BMW R80 GS and R100 GS motorcycles seeking to perform their own maintenance and repairs, enthusiasts, and professional motorcycle mechanics.
Market Competitors Era:
Honda Transalp, Yamaha XT600, Kawasaki KLR600, Suzuki DR600, Moto Guzzi V50/V75 (less direct competitors)
Motorcycle Design Philosophy:
Robustness, versatility for on-road and off-road use, shaft drive for low maintenance, boxer engine's low center of gravity.
Manual Value Proposition:
Provides essential, professional-level technical information crucial for maintaining these classic and capable machines, ensuring longevity and optimal performance.
Primary Coverage:
Comprehensive service and repair for BMW R80 GS and R100 GS models
Secondary Coverage:
Maintenance, troubleshooting, diagnostics, and general overhaul
Estimated Pages:
300-500 (typical for comprehensive workshop manuals of this era)
Type:
Workshop Manual / Service Manual / Repair Manual
Print Quality:
High-resolution scans, clear text and diagrams, suitable for printing
Binding Type:
N/A (Digital Download)
Paper Type:
N/A (Digital Download)
Searchability:
Likely text-searchable PDF for quick information retrieval
Engine:
Detailed disassembly, assembly, inspection, and repair of the boxer twin engine, including cylinder head, valves, piston, crankshaft, camshaft, timing chain, oil pump, lubrication system, and cooling (air-cooled).
Fuel System:
Carburetor systems (likely Bing CV carbs), fuel tank, fuel lines, fuel pump (if applicable), and fuel filtering.
Ignition System:
Ignition timing, coil, spark plugs, distributor (if fitted), electronic ignition components, and troubleshooting.
Transmission Drivetrain:
Clutch operation and adjustment, gearbox (5-speed), final drive, and shaft drive maintenance.
Suspension:
Front fork (telescopic, likely leading axle design) overhaul, seals, oil, and rear shock absorber (Monolever or early twin shocks depending on specific 1981 sub-models) adjustment and replacement.
Brakes:
Front and rear brake system inspection, fluid replacement, caliper overhaul, disc and pad maintenance, and hydraulic system bleeding.
Electrical System:
Wiring diagrams, battery maintenance, lighting system, starter motor, alternator, regulator, and instrument cluster troubleshooting.
Chassis Frame:
Frame inspection, fork head bearing adjustment, swingarm bearing maintenance, and general chassis component checks.
Bodywork:
Fairings, fuel tank, seat, fenders, and minor body panel removal/installation.
Routine Maintenance:
Oil changes, filter replacements, spark plug checks, air filter cleaning, chain lubrication and adjustment (if applicable for early models), brake checks, tire pressure, and lubrication points.
Troubleshooting:
Systematic diagnostic procedures for common starting, running, electrical, and mechanical issues, often presented in a 'problem-cause-solution' format.
Engine Rebuild:
Step-by-step instructions for engine disassembly, cleaning, inspection for wear, measurement of critical components, part replacement, and engine reassembly with torque specifications.
Transmission Overhaul:
Detailed procedures for gearbox disassembly, gear inspection, bearing replacement, and reassembly.
Suspension Fork Rebuild:
Instructions for replacing fork seals, springs, and oil, including proper disassembly and reassembly.
Electrical Diagnostics:
Guidance on using multimeters, interpreting wiring diagrams, and troubleshooting electrical faults in the charging, ignition, and lighting systems.
Carburetor Tuning:
Steps for adjusting idle speed, mixture, and synchronization of dual carburetors for optimal performance.
Depth:
Comprehensive; covers everything from basic rider maintenance to full engine and transmission rebuilds, including detailed technical specifications and tolerances.
Precision Measurements:
Includes critical measurements and tolerances for engine components (e.g., bore, piston clearance, valve seat runout, bearing play) requiring precision measurement tools.
Torque Specifications:
Extensive torque values for all critical fasteners across all systems.
Engine Type:
Air-cooled, horizontally opposed twin-cylinder (Boxer)
Bore X Stroke R80:
81 mm x 70.6 mm
Bore X Stroke R100:
94 mm x 70.6 mm
Displacement R80:
797.5 cc
Displacement R100:
979.7 cc
Compression Ratio Typical:
8.2:1 to 9.5:1 (varies by specific sub-model and year)
Horsepower R80 Approx:
50 PS (37 kW) at 6500 rpm
Horsepower R100 Approx:
65 PS (48 kW) at 7000 rpm
Torque R80 Approx:
57 Nm (42 lb-ft) at 5000 rpm
Torque R100 Approx:
70 Nm (52 lb-ft) at 5500 rpm
Carburetors:
2 x Bing 32mm CV (Constant Velocity) or similar
Fuel Type:
Unleaded gasoline (91 RON / 87 AKI or higher recommended)
Fuel Tank Capacity Approx:
19-20 liters (4.9-5.3 US gallons)
Gearbox:
5-speed constant mesh, sequential gearbox
Clutch:
Dry, single-plate, diaphragm spring
Final Drive:
Shaft drive, single-sided swingarm (leading to Monolever in later iterations, but likely single-sided in 1981 models)
Gear Ratios:
Specific ratios detailed in manual (typical first gear ~2.4:1, top gear ~1.0:1)
Transmission Fluid Spec:
SAE 90 Hypoid Gear Oil (check manual for exact specification and capacity, typically ~0.75L)
Oil Change Interval:
Typically every 5,000 - 7,500 km (3,000 - 5,000 miles) or annually. Check manual for exact figure.
Valve Adjustment Interval:
Every 10,000 - 15,000 km (6,000 - 9,000 miles). Requires specialized knowledge of BMW boxer valve adjustment.
Spark Plug Replacement:
Check/clean at 5,000 km, replace at 10,000-20,000 km depending on type.
Final Drive Oil Change:
Every 10,000 - 20,000 km (6,000 - 12,000 miles).
Engine Oil Type:
Multi-viscosity oil, e.g., SAE 20W-50 or SAE 15W-50, meeting API SF or SG specifications. (Manual will specify exact BMW approval or equivalent).
Engine Oil Capacity:
Approximately 2.0 - 2.2 liters (2.1 - 2.3 US quarts) with filter change. Manual is definitive.
Brake Fluid Type:
DOT 4 brake fluid (ensure compatibility with seals, manual will confirm).
Common Wear Items:
Fork seals, clutch plates, swingarm bearings, starter motor brushes, cam follower wear.
Electrical Gremlins:
Loose connections, corroded grounds, failing voltage regulators can be common with age and mileage.
Fuel System Maintenance:
Carburetor synchronization and cleaning, checking fuel petcock and lines for leaks or blockages.
Final Drive Leaks:
Potential for oil seal leaks around the driveshaft boot or wheel hub.
Bmw Motorcycle Legacy:
BMW has a long and storied history in motorcycle production, dating back to 1923. Known for engineering excellence, reliability, and shaft drive technology.
R80Gs R100Gs Genesis:
The R80 G/S (and subsequent R100 G/S) was BMW's groundbreaking entry into the dual-sport market, leveraging their established boxer twin platform with updated suspension and chassis components for off-road capability.
Key Milestones 1980S:
The R80 G/S was introduced in 1980, followed by the R100 G/S in 1987, and the introduction of the Monolever rear suspension further refined the model. The 1981 model year represents an early iteration of this influential design.
Production Period:
R80 G/S: 1980-1987; R100 GS: 1987-1996 (The 1981 models are early R80 G/S variants.)
Manufacturing Location:
Berlin, Germany (Spandau factory)
