🏷️ Basic Information

Make:

BMW

Model:

R90

Year:

1985

Vehicle Type:

Motorcycle

Chassis Code:

R90/6, R90S (Note: Manual likely covers both variants if released in 1985, though R90S was typically earlier. 1985 is a very late model year for R90 designation, suggesting potential regional variants or a typo in product naming. Assuming the manual is for a model branded as R90 in 1985.)

👋 Introduction

Positioning:

The BMW R90 series, particularly the R90S, was positioned as a premium sport touring motorcycle in its era, known for its performance, engineering quality, and comfortable ride. This manual targets owners and enthusiasts dedicated to maintaining or restoring these iconic machines.

Competitors:

In its segment, the R90 competed with other high-performance motorcycles from European and Japanese manufacturers, emphasizing rider comfort, build quality, and long-distance capability. Its shaft drive and boxer engine were distinctive features.

Manual Highlights:

Encompasses all aspects of R90 ownership, from routine upkeep to in-depth engine rebuilds. Features detailed diagrams, clear procedural steps, and essential technical data, making it an indispensable resource for preserving the legacy of the R90.

📋 Manual Details

Engine Coverage:

Complete overhaul, tuning, fuel system, ignition system, lubrication, cooling (air-cooled)

Transmission Coverage:

Gearbox disassembly, assembly, shifting mechanism, clutch service

Chassis Coverage:

Frame, suspension (front fork, rear shocks), steering head bearings, wheels, brakes (disc and drum), final drive

Electrical Coverage:

Wiring diagrams, lighting system, ignition system components, battery, charging system, starter motor, instrumentation

Bodywork Coverage:

Fairings (if applicable to R90S), fuel tank, seat, fenders, exhaust system, mounting hardware

Diagnostic Coverage:

Troubleshooting guides, fault finding procedures, common issues and solutions

Estimated Page Count:

300-500 pages (typical for a comprehensive service manual of this era and scope)

Type:

Full Service and Repair Manual

Language:

English

Format:

Digital (likely PDF), potentially available as a printed reproduction

📖 Manual Coverage

All Systems:

Engine, Drivetrain, Chassis, Electrical, Braking, Fuel, Ignition, Lubrication, Suspension, Steering, Wheels and Tires, Bodywork, Troubleshooting, Maintenance

Maintenance Procedures:

Oil changes, filter replacements, spark plug service, chain adjustment, brake adjustments, valve clearance checks, steering head bearing adjustment

Repair Procedures:

Engine rebuild, gearbox repair, carburetor overhaul, fork seal replacement, brake caliper rebuild, final drive maintenance

Diagnostic Procedures:

Troubleshooting common performance issues, ignition timing checks, carburetor synchronization, electrical system fault finding

Depth:

Comprehensive, from basic scheduled maintenance to complete engine and transmission overhauls. Includes detailed specifications, torque values, and step-by-step instructions suitable for home mechanics and professional technicians.

📊 Manual Specifications

Digital Format:

PDF (Searchable text, high-resolution diagrams, printable pages)

Print Quality:

N/A (for digital), High-resolution scans for printable versions, clear and legible diagrams

Binding Type:

N/A (for digital), Perfect bound or spiral bound (for printed reproductions)

Paper Type:

N/A (for digital), High-quality matte or glossy paper for printed versions

⚙️ Engine Specifications

Engine Type:

Air-cooled, four-stroke, horizontally opposed twin-cylinder (Boxer)

Displacement:

897 cc (for R90/6 and R90S)

Bore X Stroke:

90 mm x 70.6 mm

Compression Ratio:

9.5:1 (R90S), 8.2:1 (R90/6)

Valvetrain:

Overhead valves (OHV), pushrod actuated, 2 valves per cylinder

Horsepower:

67 hp @ 7000 rpm (R90S), 60 hp @ 6500 rpm (R90/6)

Torque:

75 Nm @ 5500 rpm (R90S), 70 Nm @ 5000 rpm (R90/6)

Carburetors:

Dell'Orto PHM 40 (R90S), Bing 32mm CV (R90/6)

Fuel Type:

Unleaded gasoline (Octane rating as per manual recommendations, typically 95 RON)

Oil Capacity:

Approx. 4 liters (including filter)

Oil Type Recommendation:

SAE 20W/50 or 10W/40 motorcycle specific oil (check manual for precise specification, e.g., API SG or higher)

Ignition System:

Breaker point ignition with dual spark plugs per cylinder (R90S), single spark ignition (R90/6)

🔧 Transmission

Type:

5-speed constant mesh, sequential manual gearbox

Optional Gearbox:

N/A (Standard across R90 models)

Drive Type:

Shaft drive (enclosed drive shaft)

Clutch Type:

Single dry plate clutch (R90/6), Twin dry plate clutch (R90S)

Gearbox Oil Type:

SAE 80W/90 hypoid gear oil (API GL-5 recommended)

📐 Dimensions

Length:

Approx. 2200 mm (varies slightly by model variant)

Width:

Approx. 850 mm (including handlebars)

Height:

Approx. 1200 mm (to top of handlebars)

Wheelbase:

Approx. 1465 mm

Dry Weight:

Approx. 200 kg (R90/6), 212 kg (R90S)

Gross Vehicle Weight:

Approx. 390 kg

Fuel Tank Capacity:

24 liters (including reserve)

🛡️ Safety Features

Safety Standard:

N/A (Motorcycle safety ratings were not standardized as they are for cars today. Focus is on operational safety and rider control.)

Braking System:

Front: Hydraulic disc brake (dual discs on R90S, single disc on R90/6), Rear: Drum brake

Suspension Type:

Front: Telescopic fork with hydraulic damping, Rear: Swingarm with dual shock absorbers

Frame Construction:

Steel tube duplex cradle frame

Lighting:

Halogen headlight, taillight, brake light, turn signals

💡 Technology Features

Infotainment System:

N/A (This era of motorcycle did not feature infotainment systems.)

Assistance Features:

N/A (No electronic driver assistance features)

🔧 Maintenance

Oil Change Interval:

Every 3,000 - 5,000 km or annually

Valve Adjustment Interval:

Every 6,000 - 10,000 km

Spark Plug Replacement Interval:

Every 10,000 - 15,000 km

Brake Fluid Change:

Every 2 years

Brake Fluid Type:

DOT 4

Final Drive Oil Type:

SAE 80W/90 hypoid gear oil (API GL-5)

Common Problems:

Kicked-in side stand damage to frame, wear in swingarm pivot bearings, carburetor synchronization issues, ignition coil failure, final drive spline wear, exhaust header leaks.

Preventative Maintenance:

Regular lubrication of swingarm and steering head bearings, checking final drive splines for lubrication and wear, ensuring proper carburetor synchronization and fuel mixture, maintaining ignition system health.

📚 Vehicle History

Bmw Motorcycle History:

BMW has a long and distinguished history in motorcycle manufacturing, dating back to the 1920s. Known for engineering excellence, robust build quality, and shaft-driven boxer engines, BMW motorcycles have a reputation for reliability and longevity.

R90 Development:

The R90 series was an evolution of BMW's successful airhead boxer line. The R90/6 was a more touring-oriented model, while the R90S was the flagship sport model, featuring aerodynamic fairing, twin disc front brakes, and higher performance tuning.

Production Years:

R90/6: 1973-1976, R90S: 1973-1976. (Note: The product listing for a 1985 R90 is unusual and may refer to a later iteration, a specific market variant, or a misprint. The core R90 design was phased out by the R100 series by the late 1970s.)

🏆 Awards & Recognition

Historical Acclaim:

The BMW R90S, in particular, was lauded for its styling, performance, and build quality, often cited as a benchmark for sport motorcycles of the 1970s and a significant contributor to BMW's reputation in motorcycling.

Owner Satisfaction:

High owner satisfaction for reliability and long-term ownership, especially when properly maintained. Many R90s are still on the road today, testament to their robust engineering.