Back to Bike FinderYears: 1940 · 1939 · 1938
BMW R51
1940Allround

BMW R51

Key specifications

Engine
494 cc
Power
24 HP
Fuel type
petrol
Fuel capacity
3.7 L
Transmission
4-speed
Front brakes
Expanding brake (drum brake)
Rear brakes
Expanding brake (drum brake)

Overview

### The Timeless Charm of the 1940 BMW R51 In the annals of motorcycle history, few machines capture the essence of post-war engineering and style as beautifully as the 1940 BMW R51. This allround motorcycle epitomizes the German maker's dedication to quality, performance, and innovative design. Positioned as a versatile option for both city commuting and long-distance touring, the R51 showcases BMW's prowess in crafting motorcycles that are not only functional but also imbued with a sense of timeless elegance. With its classic lines and robust construction, the R51 remains a sought-after gem for collectors and enthusiasts alike. At the heart of the R51 lies a potent 494cc two-cylinder boxer engine, which represents a hallmark of BMW's engineering expertise. Producing 24.07 horsepower at a modest 5600 RPM, this four-stroke powerplant delivers a satisfying blend of power and efficiency. Riders can expect a top speed of 140 km/h (87 mph), making it a capable companion on both winding roads and open highways. The engine’s 6.7:1 compression ratio and balanced bore and stroke dimensions (68mm x 68mm) contribute to its smooth performance, while the Amal carburettor ensures precise fuel delivery. The four-speed gearbox, combined with a reliable shaft drive, offers seamless power transfer, enhancing the riding experience with added confidence and control. The R51 is not just about power; it also incorporates advanced features for its time that enhance comfort and safety. The motorcycle is built on a sturdy steel single cradle frame that supports a sophisticated suspension system featuring cartridge front suspension and a twin-shock swingarm at the rear. The 200mm drum brakes at both ends provide reliable stopping power, while the 14-liter fuel tank allows for extended journeys without frequent refueling stops. Visually, the R51’s design is both functional and aesthetically pleasing, ensuring that it stands out on the road. With a weight of 182 kg (401.2 lbs), it strikes a balance between being lightweight for agility and robust for stability. ####

Pros

    Cons

    • Iconic Design: The R51's classic styling and attention to detail make it a timeless collectible, appealing to enthusiasts and casual riders alike.
    • Smooth Engine Performance: The boxer engine provides a unique riding experience with excellent low-end torque and a satisfying power delivery.
    • Comfortable Ride: The combination of a well-engineered suspension system and a comfortable seating position makes it suitable for both short commutes and longer journeys.
    • Limited Top Speed: While 87 mph is respectable, it may not satisfy those looking for high-speed performance or modern highway capabilities.
    • Drum Brakes: The use of drum brakes, while effective for the time, may not offer the stopping power and responsiveness that contemporary riders expect.
    • Kick Start Only: The traditional kick start may deter some modern riders who prefer the convenience of electric starting systems found in today's motorcycles.

    Technical details

    Source specification data

    Make
    BMW
    Model
    R51
    Category
    Allround
    Starter
    Kick
    Power
    24.07 HP (17.6 kW)) @ 5600 RPM
    Clutch
    Dry-single plate-cable operated
    Gearbox
    4-speed
    Ignition
    Battery
    Top Speed
    140.0 km/h (87.0 mph)
    Fuel System
    Carburettor. Amal
    Bore X Stroke
    68.0 x 68.0 mm (2.7 x 2.7 inches)
    Compression
    6.7:1
    Displacement
    494.00 ccm (30.14 cubic inches)
    Cooling System
    Air
    Engine Details
    Two cylinder boxer, four-stroke
    Lubrication System
    Wet sump
    Transmission Type Final Drive
    Shaft drive (cardan)
    Fuel Capacity
    14.00 litres (3.70 gallons)
    Overall Width
    815 mm (32.1 inches)
    Overall Height
    960 mm (37.8 inches)
    Overall Length
    2,130 mm (83.9 inches)
    Weight Incl Oil Gas Etc
    182.0 kg (401.2 pounds)
    Rear Tyre
    3.50-19.00
    Frame Type
    Steel single cradle
    Front Tyre
    3.50-19.00
    Rear Brakes
    Expanding brake (drum brake)
    Front Brakes
    Expanding brake (drum brake)
    Rear Suspension
    Twin shock-Swingarm
    Front Suspension
    Cartridge
    Rear Brakes Diameter
    200 mm (7.9 inches)
    Front Brakes Diameter
    200 mm (7.9 inches)