Historical Context:
BMW motorcycles of this era were renowned for their engineering quality and performance, catering to a demanding clientele and military applications.
Predecessors:
These models represented the pinnacle of BMW's motorcycle design prior to and during WWII, competing with other high-quality European manufacturers.
Features:
Flat-twin boxer engines, shaft drive, robust construction, and excellent handling for their time.
Manual Value:
Essential for owners and restorers to accurately identify and source original or reproduction parts.
Systems Covered:
Engine, Transmission, Chassis, Electrical System, Bodywork, Frame, Suspension, Brakes, Wheels, Final Drive, Fuel System, Lubrication System, Ignition System, Carburetion, Tools, Accessories
Total Pages:
Estimated 150-200 pages (based on typical parts list for multiple models)
Type:
Illustrated Parts List / Parts Catalog / Ersatzteilliste
Language:
German (with illustrated diagrams)
Format:
Likely a scanned reproduction of an original document
Engine:
Detailed breakdown of all engine components, including cylinder head, cylinders, pistons, connecting rods, crankshaft, camshaft, valves, timing gears, oil pump, and cooling system components.
Transmission:
Comprehensive parts listing for the gearbox, clutch, and associated linkage, illustrating all gears, shafts, bearings, and sealing components.
Chassis And Frame:
Diagrams and part numbers for the main frame, sub-frame, front forks, swingarm, steering head assembly, and all mounting hardware.
Electrical System:
Illustrated parts for the lighting system (headlight, taillight, indicators), ignition system (magneto, spark plugs), wiring harness, and any ancillary electrical components.
Brakes:
Parts breakdown for the drum brake systems (front and rear), including brake shoes, drums, cables, levers, and associated hardware.
Fuel And Exhaust:
Components for the fuel tank, fuel lines, carburetor(s), and the exhaust system, including mufflers and pipes.
Wheels And Tires:
Diagrams for wheels, spokes, hubs, tires, and tubes, along with associated bearings and seals.
Part Identification:
Primary function is the identification of specific part numbers for ordering and replacement.
Assembly Visuals:
Provides visual guidance on how components are assembled in their respective sub-assemblies.
Troubleshooting Assistance:
Indirectly aids troubleshooting by ensuring the correct parts are present and correctly installed.
Depth:
High (parts-specific detail, not operational procedures)
Focus:
Component-level identification and illustration for repair and restoration purposes.
Digital Format:
Likely PDF, scanned from original print.
Quality Of Scans:
Variable depending on the source scan quality; clarity of diagrams is crucial.
Original Binding:
Likely bound booklet or loose-leaf pages for older German factory manuals.
Original Paper:
Typically sturdy paper stock, designed for workshop use.
Engine Type:
Air-cooled, horizontally opposed twin-cylinder (boxer)
Bore X Stroke:
Varies by model (e.g., R51: 68mm x 74mm, R66: 72mm x 74mm, R61: 68mm x 74mm, R71: 70mm x 74mm)
Displacement:
Varies by model (e.g., R51: 494cc, R66: 596cc, R61: 494cc, R71: 710cc)
Horsepower:
Varies by model (e.g., R51: ~24 hp, R66: ~30 hp, R61: ~18 hp, R71: ~22 hp)
Torque:
Not typically specified in parts catalogs, but implied by engine displacement and tuning.
Carburetion:
Typically dual Bing or BMW-branded carburetors (specific model varies).
Fuel Type:
Gasoline (higher octane preferred for vintage engines).
Oil Type:
API SG or higher, SAE 20W-50 or SAE 30 is common for vintage flat-twins. Consult specific factory data if available.
Oil Capacity:
Approximately 1.5 - 2.0 liters (Varies by model and oil filter housing if applicable).
Ignition Type:
Magneto ignition, dual spark plugs per cylinder.
Transmission Type:
4-speed manual gearbox with constant mesh.
Gear Ratios:
Specific ratios vary by model and are detailed within the full workshop manuals, not typically in parts lists.
Drive Type:
Shaft drive to the rear wheel.
Clutch Type:
Single dry plate clutch, operated by hand lever.
Gearbox Oil:
SAE 80W/90 GL-4 gear oil is a common recommendation for vintage BMW transmissions.
Wheelbase:
Varies by model (e.g., R51/R61: ~1400mm, R66/R71: ~1450mm)
Dry Weight:
Varies by model (e.g., R51: ~170 kg, R66: ~185 kg, R61: ~175 kg, R71: ~190 kg)
Payload Capacity:
Not formally specified for civilian models, but designed for robust touring.
Crash Test Results:
N/A for the era; safety was primarily passive design and rider skill.
Braking System:
Drum brakes front and rear, requiring manual adjustment and maintenance. Effectiveness is limited by modern standards.
Frame Design:
Robust steel tube frame providing structural integrity.
Suspension:
Telescopic front forks with damping, rear swingarm with sprung/damped units (specifics vary by model).
Oil Change Interval:
Typically every 2,000-3,000 km or annually for vintage bikes, depending on usage. Consult original manual if available.
Valve Adjustment Interval:
Regular checks are crucial, often around 4,000-5,000 km, depending on wear and engine condition.
Gearbox Oil Change:
Recommended every 5,000-10,000 km or as specified.
Brake Fluid Type:
Not applicable as these bikes use cable-actuated mechanical brakes, not hydraulic fluid.
Fork Oil Type:
Varies, but typically SAE 10W or SAE 20W suspension fluid is used. Capacity is critical.
Wear And Tear:
Common issues include worn engine bearings, gearbox synchros (if applicable), clutch wear, and carburetor tuning difficulties.
Electrical Reliability:
Older wiring harnesses can degrade, leading to intermittent electrical faults. Magneto maintenance is also key.
Brake Performance:
Drum brakes are inherently less powerful than modern disc brakes and require careful adjustment and good condition linings.
Parts Availability:
Original parts are rare; reproduction parts are essential for restoration, making an accurate parts list invaluable.
Bmw Motorcycle History:
BMW has a long and storied history in motorcycle manufacturing, beginning in 1923 with the R32. Known for innovation and quality.
Predecessors:
The R51, R61, R66, and R71 built upon earlier flat-twin designs, introducing chassis and engine refinements.
Successor Models:
These models were succeeded by updated versions and the development continued through WWII and into the post-war era with models like the R51/2 and R67 series.
Production Period:
These specific models were primarily produced in the late 1930s and early 1940s, with the 1942 date referring to a specific production year or manual issue.
Military Use:
Models like the R71 were significantly adapted and produced by the Soviet Union as the M72, and also used by the German Wehrmacht during WWII.
Historical Acclaim:
BMW motorcycles of this era were widely recognized for their engineering prowess and reliability, earning them a strong reputation.
Expert Reviews:
Contemporary reviews praised their robust construction, comfortable ride, and excellent handling, especially in touring and military applications.
Production Standards:
Manufactured to high German engineering standards of the period.
