The discrepancy in engine sizes between Honda's largest off-road bike, the XR650L with a 650cc engine, and BMW's smallest off-road bike, the G 650GS with a 650cc engine, can be attributed to the different design philosophies and target markets of the two manufacturers.
Honda's Focus on Reliability and Versatility: Honda is known for its reliable and versatile motorcycles, designed to perform well in various riding conditions and offer long-term durability. The XR650L is a legendary dual-sport bike that excels both on and off the road. Honda's decision to use a 650cc engine in the XR650L is likely a result of finding a balance between power, reliability, and versatility for off-road riding.
BMW's Emphasis on Adventure Touring: BMW Motorrad, the motorcycle division of BMW, focuses on adventure touring motorcycles that offer a mix of on-road and off-road capabilities. The G 650GS, despite being marketed as an off-road bike, is designed to excel in adventure touring scenarios where riders may spend more time on paved roads. The 650cc engine size provides sufficient power for touring while still offering manageable off-road performance.
It's important to note that engine displacement alone is not the sole factor determining a bike's off-road capabilities. Factors such as power delivery, torque, weight distribution, suspension setup, and tire selection also play crucial roles in determining a motorcycle's off-road performance.
Additionally, both Honda and BMW offer larger and more off-road-focused models for those seeking greater power and performance in off-road riding scenarios. For example, Honda has the CRF450R and CRF450X, while BMW offers the F 850 GS and R 1250 GS Adventure, among others.
Ultimately, the choice of engine size for off-road motorcycles depends on the intended use, rider preferences, and the design philosophies of the respective manufacturers.