Target Audience:
BMW R90 motorcycle owners and independent repair shops seeking in-depth technical guidance.
Value Proposition:
Enables owners to perform a wide range of maintenance and repair tasks, reducing reliance on professional service and preserving the motorcycle's value.
Alternative Resources:
Owner's manuals (less technical), fragmented online forums (unverified information), and factory service bulletins (often incomplete).
Completeness:
Comprehensive coverage for all major systems, facilitating restoration and ongoing maintenance.
Detail Level:
High level of technical detail, including exploded diagrams and specific torque values.
Engine Mechanical:
Detailed rebuild and repair of the R90 engine, including cylinder head, pistons, crankshaft, camshaft, valve train, and timing components.
Engine Fuel System:
Comprehensive coverage of the carburetion system (likely Bing carburetors), fuel delivery, and tuning procedures.
Engine Ignition System:
Diagnosis and repair of the ignition system, including points, condenser, coils, and spark plugs.
Transmission:
Repair, adjustment, and rebuilding of the gearbox, clutch system, and final drive.
Brakes:
Service and overhaul of the braking system, including caliper, master cylinder, brake lines, and pad/shoe replacement.
Suspension:
Maintenance and repair of front forks and rear shock absorbers, including fluid changes and seal replacement.
Electrical System:
Wiring diagrams, troubleshooting of lighting, charging system (alternator/generator), starter motor, and battery.
Frame And Bodywork:
Information on frame components, body panel removal and installation, and general chassis maintenance.
Routine Maintenance:
Oil changes, filter replacements, spark plug service, air filter cleaning/replacement, chain adjustment, and brake adjustments.
Troubleshooting:
Diagnostic procedures for common starting issues, running problems, electrical faults, and braking anomalies.
Rebuilds:
Complete engine, transmission, and brake system rebuild procedures with torque specifications and tolerances.
Component Replacement:
Step-by-step instructions for replacing wear items like cables, bearings, seals, and gaskets.
Tuning:
Carburetor synchronization, ignition timing adjustments, and general engine performance tuning.
Depth Level:
Comprehensive, covering from basic maintenance to complete engine and transmission overhauls.
Diagnostic Capabilities:
Detailed diagnostic flowcharts and explanations for identifying and resolving mechanical and electrical issues.
Special Tools:
Identification of specialized tools required for specific procedures, often with diagrams.
Engine Type:
Air-cooled, four-stroke boxer-twin engine
Displacement:
897 cc (54.7 cu in)
Bore X Stroke:
90.0 mm x 70.6 mm
Valve Train:
Overhead valves (OHV), pushrod actuated
Horsepower Rating:
60 HP at 6,250 rpm (approximate)
Torque Rating:
75 Nm (55 lb-ft) at 4,900 rpm (approximate)
Carburetors:
Dual Bing 32/32 mm (Type 54/32)
Fuel Type:
Unleaded gasoline (minimum 91 RON / 87 AKI recommended)
Fuel Tank Capacity:
26 liters (6.87 US gallons)
Type:
5-speed manual gearbox
Clutch:
Single dry plate clutch, hydraulically actuated
Gear Ratios Estimate:
1st: 3.44, 2nd: 2.44, 3rd: 1.77, 4th: 1.39, 5th: 1.00
Final Drive Ratio:
1:3.33 (33/10 teeth)
Transmission Fluid Spec:
SAE 80W-90 GL-5 gear oil
Transmission Fluid Capacity:
200 ml (0.21 US quarts)
Oil Change Interval:
Every 5,000 km (3,000 miles) or annually.
Engine Valve Adjustment:
Every 10,000 km (6,000 miles).
Spark Plug Replacement:
Every 10,000 km (6,000 miles).
Carburetor Sync Tune:
As needed, typically every 10,000-20,000 km (6,000-12,000 miles) or if symptoms appear.
Final Drive Oil Change:
Every 20,000 km (12,000 miles).
Engine Oil Type:
SAE 20W-50 API SF or higher motorcycle specific oil.
Engine Oil Capacity:
2.5 liters (2.64 US quarts) with filter change.
Brake Fluid Type:
DOT 4 (or DOT 3 for older systems if specified).
Common Wear Items:
Valve guides, clutch wear, final drive splines, fork seals, and wiring harness degradation over time.
Typical Repairs:
Carburetor rebuilds, replacement of aging rubber components, electrical system maintenance, and fuel line replacement.
Bmw Motorcycle Division:
BMW Motorrad has a long history dating back to the early 20th century, known for quality, engineering, and distinctive boxer-twin engines.
R90 Series Legacy:
The R90 was part of BMW's successful airhead boxer series, which began with the R50/5 and evolved through models like the R75/5, R90/6, R100/7, and the R90S (a sportier variant). The R90 model itself was produced from 1973-1976, with the R90/6 and R90S being the primary designations. The 1986 manual likely covers models that are variants or continue the lineage of the R90 platform.
Production Period:
While the R90 was primarily 1973-1976, the manual for a '1986 BMW R90' suggests a specific market variant or perhaps a reference to a later model that retained R90 lineage or shared components. BMW continued production of its airhead models well into the 1990s.
Manufacturing Location:
Berlin, Germany (Spandau plant)
Bmw Motorcycle Reputation:
BMW motorcycles of this era are renowned for their build quality, durability, and rider comfort, making them highly regarded among enthusiasts and for long-distance touring.
Owner Satisfaction:
Consistently high owner satisfaction for longevity and reliability when properly maintained.
