🏷️ Basic Information

Make:

BMW

Model:

R90

Engine Code Primary:

R90/6 (likely)

👋 Introduction

Market Position:

The BMW R90 series represented BMW's entry into the larger displacement motorcycle market, positioned as a reliable, shaft-driven touring and sport-touring machine with a focus on build quality and performance.

Competitive Analysis:

Competed with other large-displacement motorcycles from manufacturers like Moto Guzzi, Kawasaki, and Honda, offering a distinctive boxer-twin engine configuration and shaft drive, appealing to riders valuing smooth power delivery and low maintenance.

Key Features Of R90:

Shaft drive, air-cooled boxer twin engine, robust chassis, comfortable riding position for touring, high-quality build.

📋 Manual Details

Model Years Covered:

1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996

Estimated Page Count:

300-500 (typical for comprehensive motorcycle service manuals of this era, specific count not provided)

Manual Type:

Full Service Repair Manual

Language:

English (presumed, standard for BMW repair manuals of this era and market)

Format:

Print (implied by 'Manual', likely a bound book)

📖 Manual Coverage

Engine Service:

Complete engine overhaul, disassembly, reassembly, valve adjustment, timing, lubrication system, cooling (air-cooled), ignition system (points, coil, spark plugs), fuel system (carburetor tuning, rebuild), exhaust system.

Transmission Drivetrain Service:

Gearbox disassembly, inspection, repair, clutch service, drive shaft maintenance, final drive inspection and lubrication.

Chassis Suspension Service:

Front fork service and overhaul, rear shock absorber replacement, swingarm bearing maintenance, steering head bearing adjustment and replacement.

Braking System Service:

Front and rear brake caliper service, master cylinder rebuild, brake line replacement, pad inspection and replacement, fluid bleeding.

Electrical System Service:

Wiring diagrams, battery maintenance, charging system (alternator, regulator), lighting systems, starter motor, ignition switch, fuses, instrument panel.

Bodywork Frame Service:

Frame inspection, fuel tank removal and installation, seat maintenance, fender replacement, fairing (if applicable) repair, general body panel adjustments.

Routine Maintenance:

Oil changes, filter replacements, spark plug replacement, air filter cleaning/replacement, chain adjustment (if applicable), lubrication points, brake fluid checks, tire pressure checks.

Troubleshooting Diagnostics:

Step-by-step diagnostic procedures for common starting issues, running problems, electrical faults, and mechanical malfunctions.

Component Rebuilds:

Detailed instructions for rebuilding carburetors, fuel pumps, brake master cylinders, wheel bearings, and other key components.

Torque Specifications:

Comprehensive list of torque values for all critical fasteners and bolts throughout the motorcycle.

Wheel And Tire Service:

Wheel bearing inspection and replacement, tire mounting and balancing, spoke tension adjustment (if applicable).

Fork And Shock Service:

Front fork seal replacement, oil level checks and changes, rear shock absorber inspection and replacement, shock linkage lubrication.

Technical Depth:

Comprehensive from basic rider maintenance to full engine and transmission rebuilds, including detailed diagnostic procedures and specifications.

Wiring Diagrams Detail:

Detailed, clear wiring diagrams for the entire electrical system, essential for troubleshooting and repair.

Intended User:

Professional mechanic, experienced DIY enthusiast, or owner dedicated to in-depth maintenance and repair.

📊 Manual Specifications

Digital File Format:

N/A (Print Manual)

Print Quality:

Professional, clear text and diagrams (typical for OEM or reputable aftermarket manuals)

Binding Type:

Perfect Bound or Spiral Bound (common for repair manuals for durability and ease of use during repairs)

Paper Type:

Durable, coated paper stock suitable for workshop environments (typical)

⚙️ Engine Specifications

Engine Type:

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

Displacement:

900 cc (approx. 897cc for R90/6)

Bore X Stroke:

90 mm x 70.6 mm (approx.)

Compression Ratio:

8.2:1 to 9.5:1 (depending on specific R90 variant and tuning)

Valve Train:

OHV, two valves per cylinder, pushrod operated

Horsepower Est:

Approx. 60-65 HP @ 6,250 RPM (R90/6)

Torque Est:

Approx. 75 Nm @ 5,000 RPM (R90/6)

Fuel Delivery:

Dual carburetors (typically Bing 32mm or 36mm depending on model and year)

Fuel Type:

Unleaded gasoline (Premium)

Oil Type:

SAE 20W-50 or SAE 10W-40 (API SG or higher recommended), specific BMW oil grades may be cited in the manual.

Oil Capacity:

Approx. 2.5 - 3.0 Liters (including oil filter)

🔧 Transmission

Transmission Type:

5-speed constant mesh, claw-shifted gearbox

Clutch Type:

Single dry plate, diaphragm spring clutch (typically)

Final Drive:

Enclosed driveshaft to rear wheel hub

Gear Ratios Primary:

Specific ratios would be detailed in the manual, typically around 1.5:1 for primary drive and various ratios for the 5 gears.

Gearbox Oil Type:

Hypoid gear oil SAE 90 (specific BMW recommendations should be checked)

📐 Dimensions

Wheelbase Est:

Approx. 1465 mm (57.7 inches) for R90/6

Dry Weight Est:

Approx. 210-220 kg (463-485 lbs) for R90/6

Gross Vehicle Weight Rating Est:

Approx. 380-400 kg (838-882 lbs)

🛡️ Safety Features

Safety Ratings Era:

Motorcycle safety standards of the late 1970s and 1980s. No formal crash test ratings like modern cars.

Active Safety Features:

Effective drum or disc brakes (depending on year/model), stable chassis, good visibility.

Passive Safety Features:

Robust frame construction, headlight, taillight, turn signals.

💡 Technology Features

Infotainment Systems:

N/A (basic analogue instrumentation typical for the era)

Ignition Type:

Contact breaker points ignition system (typical for early models), possibly electronic ignition on later iterations or aftermarket upgrades.

Charging System Type:

Bosch alternator with an external voltage regulator (typically).

🔧 Maintenance

Oil Change Interval:

Typically every 5,000 - 7,500 km (3,000 - 5,000 miles) or annually.

Valve Adjustment Interval:

Every 10,000 - 12,000 km (6,000 - 7,500 miles).

Tune Up Interval:

Regular checks of spark plugs, ignition timing, and carburetor synchronization recommended every 5,000 - 10,000 km.

Brake Fluid Type:

DOT 4 (check manual for specific DOT rating and manufacturer recommendations)

Final Drive Oil Type:

Hypoid gear oil SAE 90

Common Issues R90:

Leaking pushrod seals, worn clutch release bearings, aging electrical components, carburetor synchronization issues, output shaft seal leaks, potential wear in the swingarm pivot bearings.

Maintenance Focus Points:

Regular lubrication, checking for oil leaks, valve adjustment, carb care, and ensuring the electrical system is sound are critical for longevity.

📚 Vehicle History

Brand Heritage:

BMW has a long-standing reputation for building well-engineered, durable motorcycles, particularly known for their boxer twin engines and shaft drive systems, dating back to the early 20th century.

Model Evolution:

The R90 series, introduced in 1973 (R90/6 and R90S), was a significant development, offering increased displacement and performance over previous models. The R90/6 was the more standard, touring-oriented version, while the R90S was the sportier variant with dual front disc brakes and clip-on handlebars.

Production Years Of R90 Series:

1973-1976 (R90/6 and R90S). The manual's coverage to 1996 suggests it may also encompass later models with similar engine configurations or is potentially an extended or generalized manual for the airhead boxer series that the R90 is part of.

Manufacturing Location:

Berlin, Germany (Spandau plant)

🏆 Awards & Recognition

Motorcycle Design Awards:

The R90S model, in particular, was lauded for its styling and performance, often receiving critical acclaim from motorcycle publications of its time.

Reliability Reputation:

BMW airhead boxer motorcycles are renowned for their exceptional reliability and durability when properly maintained, often regarded as long-distance tourers and workhorses.