Segment:
Classic European Boxer-Twin Motorcycles
Target Audience:
BMW R Series owners, motorcycle mechanics, restoration specialists, enthusiasts.
Manual Quality:
Official factory manuals are the benchmark for accuracy and completeness, providing information not found in aftermarket guides.
Authenticity:
Directly from BMW factory documentation, ensuring accuracy and detail.
Comprehensiveness:
Covers all aspects of maintenance, repair, and troubleshooting for the specified models and year.
Usability:
Downloadable PDF format allows for on-demand access and printing of specific sections.
Manual Title:
BMW R80 R90 R100 1981 Factory Service Repair Manual Download PDF
Model Coverage:
BMW R80, R90, R100 models specifically for the 1981 model year.
Engine Coverage:
Covers all engine variants for the specified models, including 797cc (R80), 897cc (R90), and 979cc (R100) boxer-twin engines.
Estimated Pages:
Hundreds of pages (specific count not provided, but typical for factory manuals of this era).
Type:
Factory Service and Repair Manual
Language:
English (presumed for standard factory manuals distributed in major markets).
Engine Mechanical:
Engine assembly, disassembly, cylinder head, pistons, crankshaft, camshaft, valve timing, lubrication system, cooling system (air-cooled).
Fuel System:
Carburetor service (e.g., Bing VM), fuel tank, fuel lines, fuel pump, fuel filter.
Ignition System:
Ignition timing, spark plugs, ignition coils, ignition control unit, breaker points (if applicable).
Transmission:
Gearbox assembly, disassembly, clutch operation, shifting mechanisms, drive shaft maintenance.
Electrical System:
Wiring diagrams, battery, charging system (alternator, regulator), lighting system, starter motor, horn, instrumentation.
Chassis And Suspension:
Front forks (telescopic), rear suspension (swingarm, shock absorbers), steering head bearings.
Braking System:
Front and rear brake systems (drum or disc depending on specific model variant), brake fluid, master cylinder, calipers, lines.
Wheels And Tires:
Wheel bearing maintenance, tire specifications, rim types.
Bodywork And Frame:
Frame inspection, mounting points, fuel tank mounting, seat assembly, fenders.
Routine Maintenance:
Oil changes, filter replacements, spark plug checks, chain adjustment (if applicable), general inspections.
Troubleshooting:
Diagnostic procedures for common running issues, electrical faults, and mechanical problems.
Repair And Rebuild:
Detailed step-by-step instructions for component disassembly, repair, and reassembly of major systems.
Specifications And Tolerances:
Torque values, clearances, wear limits, and diagnostic parameters.
Special Tools:
Identification of BMW specific tools required for certain procedures.
Depth:
Comprehensive. Covers everything from basic adjustments to complete engine and transmission overhauls, including detailed electrical system diagnostics.
Type:
Air-cooled, four-stroke, boxer-twin cylinder
Displacement R80:
797 cc (48.6 cu.in.)
Displacement R90:
897 cc (54.7 cu.in.)
Displacement R100:
979 cc (59.7 cu.in.)
Bore X Stroke R80:
82 mm x 74.6 mm (3.23 in x 2.94 in)
Bore X Stroke R90:
90 mm x 70.6 mm (3.54 in x 2.78 in)
Bore X Stroke R100:
94 mm x 74.6 mm (3.70 in x 2.94 in)
Compression Ratio:
Varies by specific R80/R90/R100 variant, typically around 8.5:1 to 9.5:1
Horsepower R80:
Approx. 50 hp @ 6200 rpm
Horsepower R90:
Approx. 65 hp @ 7000 rpm
Horsepower R100:
Approx. 70 hp @ 7000 rpm
Torque R80:
Approx. 57 Nm (42 lb-ft) @ 4000 rpm
Torque R100:
Approx. 75 Nm (55 lb-ft) @ 5000 rpm
Carburetors:
Typically dual Bing VM carburetors (e.g., 32mm or 40mm depending on model variant)
Fuel Type:
Unleaded gasoline (octane rating as per original specifications)
General Configuration:
Standard motorcycle dimensions, varying slightly between R80, R90, and R100 models and their specific chassis configurations (e.g., R100RT fairing).
Dry Weight R80:
Approx. 195-205 kg (430-452 lbs)
Dry Weight R100:
Approx. 215-235 kg (474-518 lbs)
Oil Change Interval:
Typically every 5,000-10,000 km (3,000-6,000 miles), or annually, as detailed in the manual.
Valve Adjustment Interval:
Every 10,000-15,000 km (6,000-9,000 miles).
Spark Plug Replacement:
As per manual recommendation, typically every 10,000-20,000 km (6,000-12,000 miles).
Engine Oil Type:
SAE 20W-50 or SAE 15W-40 motorcycle-specific oil (verify with manual for exact year/ambient temp).
Transmission Oil Type:
API GL-5, SAE 80W-90 gear oil.
Final Drive Oil Type:
API GL-5, SAE 80W-90 gear oil.
Brake Fluid Type:
DOT 3 or DOT 4 (if equipped with disc brakes, verify specific caliper requirements).
Clutch Slave Cylinder Leaks:
Can develop leaks over time, requiring seal replacement.
Bing Carburetor Synchronization:
Requires periodic synchronization for smooth running.
Airhead Oil Leaks:
Common areas for minor oil seepage include valve cover gaskets and base seals, which can be addressed with proper torque and sealants.
Electrical Connections:
Corrosion or loosening of electrical connectors can lead to intermittent issues, requiring inspection and cleaning.
Bmw Motorrad Legacy:
BMW Motorrad has a long history of producing reliable and innovative motorcycles, with the boxer-twin engine being a signature element since 1923.
Airhead Development:
The R80, R90, and R100 series are part of BMW's 'Airhead' lineage, characterized by their air-cooled boxer engines and shaft drive. They evolved from earlier models like the R75/5 and continued through various iterations with increasing engine displacements and refinements.
Production Period:
The R80, R90, and R100 series were produced throughout the 1970s and 1980s, with the 1981 model year representing a specific point in this evolution.
