Target Audience:
BMW R90 owners and independent mechanics seeking in-depth repair and maintenance information.
Value Proposition:
Enables comprehensive DIY maintenance, repair, and restoration, saving on dealership costs and preserving vehicle integrity.
Comparison To Other Manuals:
Positioned as a 'full service' manual, implying greater depth than basic owner's manuals or condensed workshop guides.
Diagnostic Emphasis:
Highlights diagnostic capabilities, suggesting it aids in identifying and resolving problems efficiently.
Restoration Focus:
Explicitly mentions refurbishment and restoration, catering to owners looking to bring classic bikes back to life.
Engine Overhaul:
Complete engine disassembly, inspection, repair, and reassembly procedures for the BMW boxer twin engine.
Fuel System:
Carburetor tuning (likely Dell'Orto or Bing), fuel pump, fuel lines, and fuel tank maintenance.
Ignition System:
Spark plugs, ignition coils, timing adjustment, and troubleshooting for the ignition circuit.
Transmission And Drivetrain:
Gearbox inspection, repair, clutch service, driveshaft maintenance, and final drive unit procedures.
Suspension And Steering:
Front forks (likely dual shock absorber or Monolever rear), rear suspension components, wheel bearing replacement, and steering head bearing adjustment.
Brakes:
Front and rear brake system servicing, including caliper overhaul, pad replacement, brake fluid bleeding, and master cylinder inspection.
Electrical System:
Wiring diagrams, battery maintenance, lighting system troubleshooting, starter motor and alternator servicing.
Frame And Bodywork:
Chassis inspection, body panel removal and installation, seat mounting, and exhaust system maintenance.
Routine Maintenance:
Oil changes, filter replacements, chain adjustment, tire pressure checks, and general lubrication.
Troubleshooting:
Diagnostic flowcharts and common problem identification for various systems.
Rebuilding:
Detailed instructions for rebuilding major components like the engine, gearbox, and forks.
Refurbishment Restoration:
Guidance on restoring components and bringing the motorcycle back to its original condition.
Diagnostic Procedures:
Includes diagnostic steps for identifying issues within the electrical, fuel, and mechanical systems.
Technical Specifications:
Comprehensive torque values, clearances, fluid capacities, and other critical technical data.
Component Level Repair:
Detailed instructions for repairing individual components rather than just replacement.
Engine Type:
Air-cooled, four-stroke, boxer-twin cylinder engine
Engine Displacement:
897 cc (54.7 cubic inches)
Bore X Stroke:
90 mm x 70.6 mm (approximately, common for R90 variants)
Compression Ratio:
Typically 9.5:1 (R90/6) or 10.25:1 (R90S), specific to variant.
Horsepower Output:
R90/6: 60 hp @ 6500 rpm; R90S: 67 hp @ 7000 rpm (approximate, specific to variant).
Torque Output:
R90/6: 75 Nm @ 5500 rpm; R90S: 77 Nm @ 5500 rpm (approximate, specific to variant).
Carburetors:
Dual Dell'Orto PHM 38 (R90/6) or Bing 32mm CV carburetors (R90S).
Fuel Type Recommendation:
Unleaded gasoline, minimum octane rating typically 91 RON (95 AKI).
Valve Train:
Overhead valve (OHV) with pushrods and rocker arms.
Transmission Type:
5-speed manual gearbox, shaft drive.
Clutch Type:
Single dry plate, diaphragm spring clutch.
Gear Ratios:
Specific ratios will be detailed in the manual, typically optimized for touring and sport riding.
Transmission Oil Type:
SAE 80W/90 GL-4 gear oil recommended.
Transmission Oil Capacity:
Approximately 1.2 liters (1.3 US quarts).
Wheelbase:
Approximately 1465 mm (57.7 inches).
Seat Height:
Approximately 800-820 mm (31.5-32.3 inches), depending on seat and suspension.
Dry Weight:
Approximately 205-210 kg (452-463 lbs).
Gross Vehicle Weight Rating:
Not specified, but owner should consult manual for safe load limits.
Fuel Tank Capacity:
24 liters (6.3 US gallons), including a reserve of approx. 3 liters.
Crash Test Information:
Motorcycles of this era were not subjected to standardized crash testing like modern automobiles.
Braking System:
Dual disc front brake, single disc rear brake (standard on R90S, optional on R90/6). Brake calipers typically by Brembo.
Suspension System:
Telescopic front forks and a rear swingarm with dual shock absorbers (or Monolever system on later models, R90 was typically dual shock). Provides stability and handling.
Lighting System:
Halogen headlamp, taillight, brake light, and turn signals for visibility.
Infotainment Systems:
N/A - This motorcycle predates integrated infotainment systems. Focus is on core mechanical and electrical functions.
Driver Assistance Features:
N/A - No electronic driver assistance features are present on this model.
Connectivity Features:
N/A - No modern connectivity features are present.
Oil Change Interval:
Every 5,000 km (3,000 miles) or annually, whichever comes first.
Valve Adjustment Interval:
Every 10,000 km (6,000 miles).
Spark Plug Replacement:
Every 10,000 km (6,000 miles), or as needed based on condition.
Engine Oil Type:
SAE 20W/50 or SAE 10W/40 API SG or higher motorcycle-specific oil. Check manual for precise recommendations.
Brake Fluid Type:
DOT 3 or DOT 4 brake fluid.
Engine Oil Capacity:
Approximately 2.5 liters (2.6 US quarts) with filter change.
Common Wear Items:
Exhaust header gaskets, clutch plates, final drive spline lubrication, and ignition points (if applicable).
Electrical Gremlins:
Wiring harness degradation over time, particularly around connectors and heat-prone areas.
Bmw Motorcycle Legacy:
BMW has a long history of producing reliable and innovative motorcycles, particularly known for their boxer engines and shaft drive systems since the 1920s.
Predecessor Models:
The R90 series succeeded models like the R75/5 and R60/5, offering increased displacement and performance.
Successor Models:
The R90 was followed by the R100 series, which further refined the boxer engine and chassis design.
Production Years:
The R90 models were produced from 1973 to 1976.
Key Variants:
R90/6 (standard) and R90S (sport variant with fairing, twin disc front brakes, and higher compression engine).
Historical Reputation:
The BMW R90 series is highly regarded for its robust engineering, comfortable ride, and reliability, making it a popular choice for touring and classic motorcycle enthusiasts. The R90S, in particular, was a performance benchmark of its time.
Owner Satisfaction:
Generally high among owners who appreciate its classic character and mechanical simplicity.
Production Standards:
Manufactured to BMW's stringent quality standards for motorcycles of the period.
