Target Audience:
BMW motorcycle enthusiasts, DIY mechanics, restoration specialists, service technicians
Value Proposition:
Provides essential technical data and procedural guidance for maintaining and repairing the iconic BMW R90, empowering owners to perform their own work with confidence and precision.
User Benefit 1:
Detailed step-by-step repair instructions
User Benefit 2:
Comprehensive diagnostic flowcharts
User Benefit 3:
Essential technical specifications and torque values
User Benefit 4:
Clear, easy-to-understand language and diagrams
User Benefit 5:
Enables cost savings by facilitating DIY repairs
Engine:
Full overhaul, tuning, carburetion, ignition system
Transmission:
Gearbox disassembly, assembly, lubrication, clutch service
Drivetrain:
Shaft drive, final drive, universal joints
Suspension:
Front forks, rear shock absorbers, linkage adjustments
Brakes:
Hydraulic system, caliper service, disc and pad replacement
Electrical System:
Wiring diagrams, battery, charging system, lighting, ignition troubleshooting
Fuel System:
Fuel tank, fuel lines, fuel pump, carburettor tuning
Cooling System:
Air-cooled engine specifics, oil circulation
Bodywork And Frame:
Chassis inspection, body panel removal and installation
Controls:
Throttle, clutch, brake levers, foot controls
Preventative Maintenance:
Scheduled servicing, fluid changes, filter replacements, chain adjustment
Troubleshooting:
Step-by-step diagnostic guides for common and uncommon issues
Repair And Rebuild:
Detailed instructions for component disassembly, repair, and reassembly
Adjustments:
Valve clearance, carburetor synchronization, ignition timing
Electrical Diagnostics:
Component testing, fault finding for electrical systems
Specification Setting:
Torque values, clearances, fluid levels
Body Panel Repair:
Instructions for minor bodywork repairs and panel alignment
Depth:
Comprehensive: Covers everything from basic maintenance to full engine and transmission rebuilds, including advanced diagnostics.
Engine Rebuild:
Detailed steps for full engine overhaul, including piston, ring, bearing, and cylinder replacement.
Transmission Rebuild:
In-depth guidance for gearbox disassembly, inspection of gears and shafts, and reassembly.
Electrical Diagnostics Level:
Advanced diagnostics for electrical faults, including troubleshooting wiring harness issues and component testing.
Engine Type:
Air-cooled, four-stroke, boxer-twin cylinder
Bore X Stroke:
90 mm x 70.6 mm
Horsepower Max:
60 hp (44 kW) at 6,250 rpm
Torque Max:
70 Nm (52 lb-ft) at 5,000 rpm
Valve Adjustment Method:
Screw and locknut adjustment
Carburetors:
2 x Bing 32mm (Type 54/40/101 or similar)
Fuel Type:
Unleaded gasoline, minimum 91 octane (RON+MON)/2
Type:
Battery-coil, distributor ignition (or electronic ignition for some variants)
Configuration:
Overhead valves (OHV), pushrod actuated
Type:
5-speed manual gearbox
Clutch:
Single dry plate, diaphragm spring
Drivetrain:
Shaft drive to rear wheel
Gear Ratios Final Drive:
Approx. 3.36:1 (11/37 teeth)
Gearbox Oil:
SAE 80W/90 Hypoid Gear Oil (API GL-5)
Gearbox Oil Capacity:
Approx. 1.3 liters (1.4 US qt)
Safety Standards:
Designed to meet contemporary safety regulations for motorcycles
Braking System:
Dual front disc brakes, single rear disc brake
Suspension Stability:
Telescopic front forks, BMW Motorrad swing arm with adjustable rear shocks for improved handling and stability
Frame Construction:
Robust steel tube frame for structural integrity
Oil Change Interval:
Every 5,000 km (3,000 miles) or annually
Valve Adjustment Interval:
Every 10,000 km (6,000 miles)
Spark Plug Replacement Interval:
Every 10,000 km (6,000 miles)
Engine Oil Type:
SAE 20W-50 Motorcycle Oil (Mineral or Synthetic)
Engine Oil Capacity:
Approx. 2.5 liters (2.6 US qt)
Brake Fluid Type:
DOT 4 Hydraulic Brake Fluid
Common Issue 1:
Carburetor synchronization drift
Common Issue 2:
Wear in final drive splines
Common Issue 3:
Leaking fork seals
Common Issue 4:
Aging electrical connectors and wiring insulation
Manufacturer:
Bayerische Motoren Werke AG (BMW)
Motorcycle Division History:
BMW has a long and storied history in motorcycle manufacturing, dating back to the early 20th century, renowned for engineering excellence and reliability.
Predecessors:
Evolution from earlier R-series models, building on the successful boxer engine platform.
Significance:
The R90 Series represented a significant step in BMW's motorcycle development, offering increased power and refinement, making it a popular choice for touring and sport riding.
R90S Distinction:
The R90S variant, with its distinctive fairing, sportier camshafts, and dual disc front brake, offered enhanced performance.
Production Years:
1973-1976 (R90/6 and R90S variants)
Manufacturing Location:
Berlin-Spandau, Germany
