🏷️ Basic Information

Make:

BMW

Model:

R100

Year:

1991

Chassis Code:

R100GS, R100R, R100RS, R100RT, R100S, R100T (Common chassis variations for the R100 line around this era, specific to the 1991 model year variants)

👋 Introduction

Market Context:

The BMW R100 series represents iconic German engineering in the motorcycle world, known for its robust boxer engines, reliable shaft drive, and touring capabilities. This manual caters to owners seeking to maintain and restore these classic machines.

Comparison To Peers:

Positioned against contemporary large-displacement motorcycles from brands like Honda (e.g., GL series), Yamaha (e.g., XS series), and Moto Guzzi, the R100 offered a unique blend of performance, durability, and sophisticated engineering. This manual provides the depth needed to understand its specific technical advantages.

Manual Value Proposition:

Enables DIY maintenance and repairs, reduces reliance on potentially expensive dealership service, empowers owners for restoration projects, and provides essential data for collectors and enthusiasts.

📋 Manual Details

Primary Coverage:

Comprehensive service, repair, maintenance, and restoration for the 1991 BMW R100 series motorcycles.

Variant Coverage:

Likely covers variants such as R100GS (dual-sport), R100R (roadster), R100RS (sport-touring), R100RT (touring), and R100S/T. Specific inclusion depends on the exact scope of the manual.

Estimated Pages:

Approximately 400-600 pages (typical for a full factory-level service manual covering multiple variants).

Type:

Full Service Repair Manual

Language:

English (likely, as standard for international sales)

Format:

Digital (PDF) or Printed Book (as indicated by 'product description')

📖 Manual Coverage

Engine:

Detailed breakdown of the BMW boxer twin engine: cylinder heads, valves, pistons, crankshaft, camshaft, timing, lubrication system, cooling system (air-cooled), fuel delivery (carburetor specifications and tuning).

Transmission:

5-speed manual gearbox, clutch system (dry single plate), final drive (shaft drive system), maintenance, disassembly, and reassembly procedures.

Electrical System:

Ignition system (points or electronic depending on specific R100 sub-model variant), charging system (alternator, rectifier/regulator), battery, lighting circuits, starter motor, wiring diagrams for all standard equipment.

Chassis And Suspension:

Front fork (telescopic, potentially dual-chamber or monolever depending on model variant), rear suspension (swingarm, monolever or twin shock absorber), wheel bearing maintenance, steering head bearing adjustment.

Brakes:

Front and rear brake systems (disc brakes with hydraulic actuation), brake caliper overhaul, master cylinder service, brake fluid specifications and bleeding procedures.

Fuel System:

Carburetor identification (e.g., Bing 32/40/42), fuel tank, fuel lines, fuel pump (if applicable), jetting specifications, mixture adjustments.

Bodywork And Trim:

Body panel removal and installation, seat, fuel tank, fairings (if equipped on RS/RT models), fenders, instrument cluster.

Exhaust System:

Maintenance and repair of exhaust headers, mufflers, and gaskets.

Wheels And Tires:

Wheel bearing maintenance, tire pressure recommendations, and tire replacement procedures. Includes specifications for rim sizes and spoke tensioning if applicable.

Maintenance:

Scheduled maintenance, oil changes, filter replacements, spark plug checks and replacement, valve clearance adjustment, carburetor synchronization, brake system bleeding, lubrication points.

Troubleshooting:

Diagnostic charts for common starting problems, engine performance issues, electrical faults, and braking system malfunctions.

Repair And Rebuild:

Complete disassembly and reassembly procedures for major components, engine overhaul, gearbox repair, suspension rebuild, brake system overhaul.

Diagnostic Procedures:

Step-by-step diagnostic flowcharts for common electrical issues, engine performance problems, and chassis component malfunctions. Includes troubleshooting electrical shorts, open circuits, and intermittent faults.

Torque Specifications:

Extensive list of precise torque values for all critical fasteners, including engine internals, chassis bolts, brake components, and suspension mounts.

Wiring Diagrams:

Detailed, factory-level wiring schematics covering all electrical systems, including engine management, lighting, ignition, and accessories.

Depth:

Expert-level detail suitable for professional mechanics and experienced home mechanics. Includes precise torque specifications, tolerances, and diagnostic procedures.

Rebuild Guides:

Comprehensive guides for complete engine rebuilds, transmission overhauls, and suspension component refurbishment, including special tool requirements.

📊 Manual Specifications

Digital Format Features:

Searchable text, hyperlinked table of contents, printable pages, high-resolution diagrams and illustrations.

Print Quality Description:

High-quality reproductions of original factory diagrams and clear, legible text for easy understanding of complex procedures.

Binding Type:

If printed: Spiral-bound or Perfect-bound for lay-flat usability in a workshop environment.

Paper Type:

If printed: Durable, often glossy or semi-gloss paper for resistance to workshop grime and oil.

⚙️ Engine Specifications

Engine Type:

Air-cooled, four-stroke, horizontally opposed twin-cylinder boxer engine.

Displacement:

980 cc (for most R100 variants)

Bore X Stroke:

94.0 mm x 70.6 mm (typical)

Compression Ratio:

Typically 8.5:1 or 9.0:1, depending on specific model and tuning.

Valve Train:

Overhead camshaft (driven by pushrods and rocker arms) per cylinder head.

Lubrication System:

Wet sump with oil cooler integrated into the engine casing or as a separate unit (depending on model variant). Oil filter: cartridge type.

Horsepower Range:

Approximately 65-70 hp (at 7000-7250 rpm), depending on variant and tuning.

Torque Range:

Approximately 75-79 Nm (55-58 lb-ft) at 5000-6000 rpm.

Carburetors:

Dual Bing constant-velocity carburetors (e.g., 32mm, 40mm, or 42mm depending on model variant).

Fuel Type:

Unleaded gasoline, minimum 91 RON (Research Octane Number).

🔧 Transmission

Gearbox:

5-speed constant mesh, sequential shifting.

Clutch:

Dry, single-plate, diaphragm spring actuation.

Drive Type:

Shaft drive to rear wheel.

Gear Ratios:

Specific gear ratios are detailed within the manual for each model variant.

Final Drive Ratio:

Typically 1:3.33 (11/33 teeth) or similar, detailed in manual.

📐 Dimensions

Wheelbase:

Varies by model variant (e.g., R100GS approx. 1450mm, R100RS/RT approx. 1465mm).

Seat Height:

Varies significantly by model (e.g., R100GS is higher than R100R/RS/RT).

Dry Weight:

Varies by model variant (e.g., R100GS approx. 210kg, R100R approx. 195kg, R100RT approx. 230kg).

Gross Vehicle Weight Rating:

Details provided in manual, dependent on specific model and load capacity.

Fuel Capacity:

Typically 19-26 liters (approx. 5-7 gallons) depending on the fuel tank size for different models.

🛡️ Safety Features

Frame Construction:

Steel tube frame (Duplex cradle design), offering rigidity and durability.

Lighting:

Halogen headlight, integrated turn signals, tail light, brake light.

💡 Technology Features

Instrument Cluster:

Analog speedometer, tachometer, odometer, trip meter, fuel gauge, engine temperature warning light, oil pressure warning light, neutral indicator, turn signal indicators.

ABS:

ABS was optional on some R100 variants in later years, but typically not standard on 1991 models. Manual will detail ABS system if equipped.

Charging Ports:

Not typically equipped with standard accessory power outlets; manual may cover aftermarket installations.

🔧 Maintenance

Oil Change Interval:

Typically every 3,000-5,000 miles (5,000-8,000 km) or annually, as specified in the manual. Includes gearbox and final drive oil change intervals.

Valve Adjustment Interval:

Recommended every 6,000-10,000 miles (10,000-16,000 km) or as needed based on sound.

Spark Plug Replacement Interval:

Typically every 6,000-12,000 miles (10,000-20,000 km), depending on plug type and condition.

Engine Oil Specification:

API SG or higher, SAE 20W-50 or SAE 10W-40 (depending on climate). Refer to manual for precise recommendations. Common spec: Castrol GTX 20W-50.

Gearbox Oil Specification:

API GL-5, SAE 75W-90 or 80W-90 gear oil. Capacity: approx. 1.2 liters. Common spec: Motul Gear 300 75W-90.

Final Drive Oil Specification:

API GL-5, SAE 80W-90 gear oil. Capacity: approx. 0.25 liters. Common spec: Castrol EPX 80W-90.

Brake Fluid Specification:

DOT 4 or DOT 3 (check caliper markings and manual) glycol-based brake fluid.

Fork Oil Specification:

Specific viscosity and quantity detailed in manual. Common fork oil: SAE 15W. Capacity: approx. 160-180 ml per fork leg.

Common Wear Items:

Valve stem seals, clutch friction plates, output shaft seal, front fork seals, steering head bearings, exhaust header gaskets, and aging electrical connectors.

Carburetor Tuning:

Bing carburetors can require periodic synchronization and jet cleaning for optimal performance and fuel economy.

Charging System:

Older voltage regulators (especially mechanical types) can be prone to failure; manual covers testing and replacement with modern electronic units.

📚 Vehicle History

Bmw Motorcycle Legacy:

BMW has a long history of producing robust, reliable motorcycles, particularly known for their boxer engines and shaft drive since the 1920s. The R100 builds upon this extensive heritage.

R100 Lineage:

The R100 series, introduced in the late 1970s as an evolution of the R90 and R80 series, represented BMW's successful entry into larger displacement touring and sport-touring segments. The 1991 models are part of the later production runs, often featuring updates like the Monolever rear suspension on some variants.

Monolever Rear Suspension:

The introduction of the Monolever rear suspension on models like the R100GS and R100R was a significant engineering advancement, simplifying the rear end and improving handling over earlier twin-shock designs.

Production Period:

The R100 series was produced from 1976 to 1996, with the 1991 models being a significant iteration within this long production run.

🏆 Awards & Recognition

Motorcycle Journal Reviews:

While specific 'awards' for a 1991 model year manual are rare, the R100 series consistently received praise in contemporary motorcycle publications for its durability, comfort, and all-around competence as a touring machine.