During the 1960s to the 1980s, several European motorcycle manufacturers, particularly those from the United Kingdom, chose to position the chain drive on the right side of the motorcycle. This decision was primarily driven by technical and design considerations that were prevalent during that era. Here are some of the reasons behind this choice:
Design Heritage: British motorcycle manufacturers, such as Triumph, BSA, Norton, and others, had a long-standing tradition of placing the primary drive, which included the clutch and chain, on the right-hand side. This design heritage influenced subsequent models and became a distinctive characteristic of British motorcycles.
Engine Layout: Many British motorcycles of that period featured vertical-twin engines, where the cylinders were oriented longitudinally with the crankshaft running from front to back. Placing the chain drive on the right side allowed for a more direct power transfer from the crankshaft to the transmission, which simplified the design and reduced power losses.
Gearbox Design: The gearbox on these motorcycles was typically separate from the engine and positioned on the left side. Placing the chain drive on the right allowed for a more efficient transfer of power from the gearbox to the rear wheel, as it involved fewer directional changes and resulted in less angularity for the chain.
Frame Design: The frame design of British motorcycles often had a single downtube running from the steering head to the engine. Placing the chain drive on the right side allowed for a more compact and aesthetically pleasing frame design, as the chain could pass directly from the engine sprocket to the rear wheel sprocket without interference from the frame.
Tradition and Standardization: The choice of placing the chain drive on the right side was also influenced by the desire to maintain consistency and standardization within the British motorcycle industry. By adhering to the established convention, manufacturers could ensure compatibility between different components and reduce manufacturing complexities.
It's worth noting that this design choice was not exclusive to European motorcycles, as several American motorcycles, such as Harley-Davidson, also followed a similar pattern during that era. However, over time, as motorcycle designs evolved and global standardization increased, the left-side chain drive configuration became more prevalent due to factors like improved engineering techniques, increased global exchange of ideas, and the adoption of common industry practices.
It's important to remember that this information is based on historical trends and generalizations, and individual motorcycle models may have had variations or exceptions to these design practices.