The Vintage Motorcycles
Specialists in antique, classic, veteran and vintage motorcycles.
Specialists in antique, classic, veteran and vintage motorcycles.
The 1926 BMW R42 was the successor to the groundbreaking BMW R32 and represented the first major development of BMW's original Boxer motorcycle design. Introduced in 1926, the R42 retained the 494cc side-valve Boxer engine, shaft final drive, three-speed gearbox, and tubular frame concept of the R32 while delivering a substantial increase in power.
Its 494cc air-cooled horizontally opposed twin-cylinder engine produced 12 horsepower at 3,400 rpm, compared with 8.5 horsepower for the R32. With a top speed of approximately 95 km/h, the R42 was intended primarily as a dependable road and touring motorcycle rather than a high-performance sporting machine.
The R42 used BMW's M43 engine with a 68 x 68 mm bore and stroke and a 4.9:1 compression ratio. The side-valve configuration and conservative compression ratio reflected BMW's emphasis on durability and dependable operation with the fuels and mechanical technology available during the 1920s.
BMW retained the basic twin-loop tubular steel frame of the R32, but the R42 received chassis refinements including a five-laminae plate-spring front suspension and an improved braking arrangement. The new cardan-shaft brake replaced the wedge-shaped shoe brake used on the earlier R32.
The R42 also retained BMW's shaft final drive, with power transferred from the three-speed gearbox to the rear wheel through an enclosed cardan shaft. Alternative final-drive ratios were available for sidecar operation.
BMW produced the R42 from 1926 through 1928, with 6,502 examples built. A major factor in its success was its lower purchase price of 1,510 Reichsmarks, approximately 30 percent below the R32.
The 1926 BMW R42 is therefore an important milestone in BMW motorcycle history. It took the fundamental engineering principles established by the R32 and turned them into a more powerful, more refined, and considerably more commercially successful motorcycle.
BMW introduced the R42 in 1926, approximately three years after the company's first production motorcycle, the R32. The new model was developed as the successor to the R32 and retained the basic architecture that had established BMW's reputation in motorcycle engineering.
The R32 had introduced BMW's horizontally opposed Boxer engine, longitudinal crankshaft, shaft final drive, and tubular frame. Rather than abandoning this successful formula, BMW refined it for the R42.
The most important change was the increase in engine output. The R42 retained a 494cc side-valve Boxer but produced 12 horsepower at 3,400 rpm, giving it 50 percent more power than the R32.
The engine also received revised cylinder-head construction, with separate alloy cylinder heads contributing to the updated design. These changes improved the engine while preserving its simple and durable side-valve configuration.
BMW also revised the chassis and braking system. The frame remained largely unchanged, but the R42 introduced a five-laminae front plate spring and a new brake acting at the cardan shaft.
The most important commercial change was the price. BMW reduced the R42's price to 1,510 Reichsmarks, approximately 30 percent below the R32. BMW Group Classic records that production more than doubled compared with the R32, reaching more than 6,500 motorcycles.
BMW's production records give the R42 a production period of 1926 to 1928 and a total production figure of 6,502 motorcycles.
The 1926 model year is especially significant because it represents the beginning of the R42 production run and the first major evolution of BMW's original Boxer motorcycle following the introduction of the R32.
The 1926 BMW R42 is powered by the M43, an air-cooled four-stroke horizontally opposed two-cylinder Boxer engine with a displacement of 494cc.
The engine has a 68 x 68 mm bore and stroke, giving it a square configuration. The compression ratio is 4.9:1, a conservative specification appropriate for the fuels and operating conditions of the period.
The M43 uses side-valve distribution and produces 12 horsepower at 3,400 rpm. The engine was designed around steady and dependable power delivery rather than high engine speeds or racing performance.
Fuel is supplied through a single BMW Spezial carburetor. BMW technical references specify a two-valve 22mm BMW Spezial carburetor for the R42.
The engine uses forced-feed lubrication supplied by a gear-driven oil pump. This system provided controlled lubrication to the engine and supported the durability required from a motorcycle intended for regular road use.
The R42 reaches a top speed of approximately 95 km/h. BMW Group Classic lists the same 95 km/h maximum speed for the production model.
The horizontally opposed cylinder arrangement keeps the engine mass low in the chassis while exposing both cylinder assemblies directly to cooling airflow. This Boxer configuration became one of the defining characteristics of BMW motorcycles.
The R42 uses a three-speed manual gearbox with hand-operated shifting. The specified gear ratios are approximately 2.49:1 in first gear, 1.50:1 in second, and 1.08:1 in third.
The gearbox is connected to the engine through a dry single-plate clutch. The simple three-speed arrangement was appropriate for the R42's 12-horsepower engine and touring-oriented purpose.
Power is transmitted to the rear wheel through BMW's cardan shaft final drive. The shaft runs longitudinally from the gearbox to the rear bevel-drive assembly, creating an enclosed alternative to the exposed chain drives commonly used by motorcycles of the period.
Solo motorcycles could use a rear-wheel ratio of approximately 4.53:1 or 3.80:1. BMW also provided lower gearing for sidecar use, with ratios of approximately 6.27:1 or 5.70:1.
The lower sidecar gearing increased the mechanical advantage at the rear wheel and helped compensate for the additional weight and rolling resistance of a sidecar combination.
The shaft-drive system was one of the most distinctive elements of BMW's early motorcycle engineering. The R42 continued the concept introduced with the R32 and helped establish shaft drive as a defining BMW characteristic.
The R42 uses a twin-loop steel tubular frame that remained closely related to the chassis of the R32. BMW retained this proven structure while making targeted improvements to the running gear.
The front suspension uses a five-laminae plate-spring system. The leaf-spring arrangement provides front-wheel movement while maintaining a simple and robust mechanical design.
The rear wheel is rigidly mounted in the frame. There is no separate rear-wheel suspension, with rider comfort partly provided by the spring-loaded saddle and the relatively large tires.
The R42 was available with deep-bed wheel rims measuring 19 x 3 or 21 x 2.5. Tire specifications varied with the wheel configuration, including 26 x 3.5 and 27 x 2.75 sizes.
The front brake is a 150mm drum brake. At the rear, an external shoe brake operates on the gearing at the cardan shaft.
The R42 has an approximately 1,410mm wheelbase and dimensions of approximately 2,100mm in length, 800mm in width, and 950mm in height. The motorcycle weighs approximately 126kg with a full fuel tank.
The chassis was designed to provide stability and durability rather than the suspension performance expected from later BMW motorcycles. Its simple construction was well suited to the road conditions of the 1920s.
The 1926 BMW R42 has the unmistakable appearance of an early BMW Boxer motorcycle, with an exposed horizontally opposed engine, tubular twin-loop frame, large wire wheels, broad mudguards, and an upright riding position.
The Boxer engine dominates the motorcycle visually. The two cylinders extend horizontally from opposite sides of the crankcase and remain exposed to the surrounding airflow.
The tubular frame is clearly visible beneath and around the engine. This construction gives the R42 the straightforward mechanical appearance typical of BMW motorcycles before the company introduced its later pressed-steel frames.
The large wheels and substantial mudguards were designed for practical road use. Motorcycle roads during the 1920s could be uneven and poorly surfaced, making large wheels and a stable chassis important characteristics.
The cardan shaft is another defining visual feature. Its enclosed housing runs from the gearbox toward the rear wheel and gives the motorcycle a clean final-drive arrangement compared with exposed chain systems.
The overall design is functional rather than decorative. The R42 exposes its major mechanical components and makes the engineering itself an important part of the motorcycle's appearance.
The R42 was developed directly from the BMW R32 and retained the core engineering formula that made the earlier motorcycle historically important.
Both motorcycles use a 494cc horizontally opposed Boxer engine, longitudinal crankshaft, three-speed gearbox, shaft final drive, and tubular frame. The R42, however, introduced significant improvements in power, braking, and suspension.
The increase from 8.5 horsepower to 12 horsepower represented a substantial improvement in performance while maintaining the side-valve engine architecture.
The revised engine also used separate alloy cylinder heads, while the chassis received a five-laminae front spring and improved braking arrangement.
BMW's new cardan-shaft brake replaced the previous wedge-shaped shoe brake of the R32. This was an important practical improvement and helped modernize the motorcycle's braking system.
The R42 also became considerably more affordable. Its 1,510 Reichsmark price was approximately 30 percent lower than the R32, helping BMW more than double production volume compared with its first motorcycle.
The R42 therefore represents the point at which BMW's original Boxer concept evolved from a pioneering engineering design into a more mature and commercially successful motorcycle.
The R42 was suitable for sidecar operation and could be equipped with dedicated lower final-drive gearing to compensate for the additional load.
Solo final-drive ratios were approximately 4.53:1 or 3.80:1, while sidecar configurations used approximately 6.27:1 or 5.70:1. The lower gearing increased rear-wheel torque and made the motorcycle better suited to moving the heavier combination.
The 494cc Boxer engine's low-revving characteristics were appropriate for sidecar use. Although the 12-horsepower output was modest, the engine was designed to provide steady road performance rather than high-speed acceleration.
The sturdy tubular frame and rigid rear chassis also provided a suitable foundation for sidecar operation. The motorcycle's relatively long wheelbase and large wheels contributed to stability.
Sidecars were an important part of the motorcycle market during the 1920s because they provided practical passenger and luggage capacity. The R42's ability to operate with a sidecar therefore increased its usefulness beyond solo touring.
The availability of specific sidecar gearing demonstrates that BMW considered sidecar operation an integral part of the R42's intended use rather than simply an aftermarket possibility.
The R42 has the mechanical character of a straightforward late-1920s touring motorcycle. Its 494cc side-valve Boxer engine is low-revving, conservative, and designed around dependable road operation.
The 4.9:1 compression ratio and 3,400-rpm power peak reflect the technology and fuel available during the period. The engine is not designed for high-speed operation but instead provides steady power for normal touring.
The three-speed hand-shift gearbox is simple and direct. Its limited number of ratios reflects the modest performance requirements of the motorcycle and the mechanical standards of the period.
The cardan final drive gives the R42 a distinctive mechanical character and reduces the external maintenance associated with chain-drive systems.
The five-laminae plate-spring front suspension and rigid rear frame provide a distinctly early motorcycle riding experience. The large wheels and stable chassis help the motorcycle maintain a composed attitude on period roads.
The R42's appeal lies in its combination of mechanical simplicity, durability, and innovative drivetrain design. It represents BMW's early engineering philosophy before later developments transformed motorcycle suspension, braking, and engine technology.
The R42 was a major commercial success for BMW during the 1920s. BMW Group Classic states that the model's 30-percent price reduction helped its production volume more than double compared with the R32, reaching more than 6,500 motorcycles.
BMW production records specify 6,502 R42 motorcycles built between 1926 and 1928. This made the R42 one of the most successful BMW motorcycles of the decade.
The combination of improved performance and lower price was central to the model's success. Buyers received BMW's advanced Boxer and shaft-drive architecture while paying substantially less than for the original R32.
The R42 therefore helped BMW expand its motorcycle customer base and establish a stronger commercial foundation for subsequent models.
Its success also allowed BMW to develop a broader motorcycle range. The company could build on the R42's 494cc platform while offering more sporting alternatives such as the R47 and later touring models such as the R52.
The R42 demonstrates that BMW's early motorcycle success depended not only on technical innovation but also on practical engineering, reliability, and competitive pricing.
The R42 helped establish the Boxer engine as the central architecture of BMW's motorcycle range. The horizontally opposed twin-cylinder layout introduced with the R32 was refined rather than abandoned.
The 494cc displacement became an important foundation for BMW's late-1920s motorcycle development. The company used related engineering concepts for both touring and sporting motorcycles.
The R47, introduced in 1927, represented the sporting direction of the 494cc platform, using an overhead-valve engine and producing 18 horsepower at 4,000 rpm. The R42 remained the more conservative side-valve touring model.
This distinction allowed BMW to broaden its product range without abandoning the common Boxer and shaft-drive architecture that defined the company's early motorcycles.
The R42 therefore had an influence beyond its own production period. It helped establish the mechanical and commercial foundation from which BMW developed increasingly sophisticated motorcycles during the late 1920s and early 1930s.
The 1926 BMW R42 is particularly significant to collectors because it represents the first production year of the successor to BMW's pioneering R32.
BMW produced 6,502 R42 motorcycles between 1926 and 1928. Despite this relatively strong production figure for the period, surviving original motorcycles are now uncommon after almost a century of use, modification, restoration, and loss.
Originality is especially important when evaluating an R42. Correct M43 engine components, separate alloy cylinder heads, the twin-loop tubular frame, BMW Spezial carburetor, Bosch magneto ignition, three-speed gearbox, five-laminae spring fork, 150mm front drum brake, cardan-shaft brake, wheels, fuel tank, and controls all contribute to historical authenticity.
Matching engine and frame numbers can help determine whether a surviving example retains its original major components. Period registration documents, photographs, factory records, service documentation, and restoration records can provide additional evidence of provenance.
The frame should be inspected for corrosion, cracks, brazed repairs, distortion, or later modifications. The engine, gearbox, clutch, driveshaft, bevel drive, suspension, brakes, wheels, and electrical components should also be assessed carefully.
Because the R42 was designed as a practical road motorcycle and was capable of sidecar use, surviving examples may have experienced substantial working service. An R42 retaining correct early components and documented history is therefore particularly interesting to collectors of BMW's earliest Boxer motorcycles.
The 1926 model is especially desirable from a historical perspective because it represents the beginning of the R42 production run and the first major refinement of BMW's original motorcycle formula.
The 1926 BMW R42 matters because it was the first major evolution of BMW's original R32 motorcycle and helped transform the company's pioneering Boxer concept into a successful production formula.
Its 494cc side-valve Boxer engine produced 12 horsepower at 3,400 rpm, giving the R42 50 percent more power than the R32 while retaining the same fundamental engine architecture.
The motorcycle also introduced important chassis and braking refinements. The five-laminae front spring improved the running gear, while the new brake at the cardan shaft replaced the earlier wedge-shaped shoe brake.
The R42 retained BMW's shaft final drive, a feature that would become one of the company's most recognizable mechanical characteristics. The combination of Boxer engine and shaft drive was already clearly established by 1926.
Its lower price was equally important. At 1,510 Reichsmarks, the R42 cost approximately 30 percent less than the R32, helping BMW more than double production to 6,502 motorcycles.
The R42 also offered sidecar capability with dedicated lower gearing, making it useful for passenger carrying and practical touring.
For collectors and historians, the 1926 BMW R42 represents a crucial link between the pioneering R32 and the increasingly sophisticated BMW motorcycles that followed. It is the motorcycle that demonstrated how BMW could refine its innovative Boxer architecture while making it more accessible to a wider market.
This 1926 BMW R42 represents the first production year of the successor to BMW's groundbreaking R32 and one of the most important early stages in the development of the BMW Boxer motorcycle.
Its 494cc M43 side-valve Boxer engine produces 12 horsepower at 3,400 rpm and gives the motorcycle a top speed of approximately 95 km/h. The engine retains the conservative and durable characteristics of BMW's original Boxer design while delivering 50 percent more power than the R32.
The R42 also features BMW's characteristic shaft final drive, three-speed manual gearbox, tubular twin-loop frame, five-laminae plate-spring front suspension, and 150mm front drum brake. A dedicated lower final-drive ratio was available for sidecar use.
BMW produced 6,502 R42 motorcycles between 1926 and 1928. The model's success was helped by a 30-percent reduction in price compared with the R32, making the R42 considerably more accessible while retaining BMW's distinctive Boxer and shaft-drive engineering.
As a 1926 first-year example, the R42 represents an especially important point in BMW motorcycle history. It shows the company's original Boxer concept evolving into a more powerful, refined, and commercially successful motorcycle.
For collectors, the 1926 BMW R42 offers the opportunity to own an important pre-war BMW that connects the pioneering R32 with the more advanced Boxer motorcycles of the late 1920s and 1930s. Contact us for additional photographs, detailed specifications, frame and engine numbers, service history, originality assessment, provenance, restoration details, and purchasing information for this 1926 BMW R42.
Explore more BMW motorcycles from the pre-war and classic eras.
The Vintage Motorcycles presents a curated selection of historically significant German vintage motorcycles, with BMW representing one of the most technically influential manufacturers in modern motorcycle engineering. From its early post-World War I developments to the establishment of a distinct mechanical identity, BMW played a central role in redefining structural balance, drivetrain efficiency, and long-distance reliability.
This collection includes machines from BMW alongside other notable German motorcycle manufacturers, each contributing to a tradition of precision engineering and mechanical durability. BMW motorcycles are best understood within the broader context of pre-war motorcycle engineering (1900-1939), particularly during the interwar period when the brand introduced its defining boxer engine and shaft-drive system, as well as through post-war motorcycle development, where these engineering principles were further refined into globally recognized touring platforms.
Each motorcycle within our collection is sourced based on historical provenance, structural originality, and mechanical integrity, ensuring alignment with museum-grade preservation standards. For collectors seeking acquisition opportunities, available machines can be explored through our global vintage motorcycle inventory, supported by a fully insured international shipping service.
BMW engineering is defined by a systematic and highly disciplined approach to mechanical design, emphasizing structural balance, drivetrain efficiency, and long-term reliability. The introduction of the horizontally opposed boxer engine, combined with shaft-drive transmission, established a unique engineering architecture that distinguished BMW from most contemporaries.
From early models such as the R32 to later pre-war and post-war developments, BMW motorcycles illustrate a continuous evolution focused on refinement rather than radical change. This consistency reflects a broader German engineering philosophy, where precision manufacturing, functional design, and mechanical longevity take precedence, positioning BMW as a cornerstone in the study of global motorcycle engineering history.
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