The Royal Enfield company may suggest not keeping a full tank of fuel in their motorcycles for a few reasons:
Weight Distribution: Motorcycles, including Royal Enfield models, are designed with a specific weight distribution in mind to ensure optimal handling and stability. Carrying excess weight at the rear of the motorcycle, such as a full fuel tank, can impact the balance and handling characteristics of the bike, especially during turns or maneuvers. By recommending not to keep a full tank, the company aims to maintain the intended weight distribution for better control and maneuverability.
Safety and Stability: A full tank of fuel adds additional weight to the motorcycle, which can affect its overall stability, especially at higher speeds. The added weight can increase the bike's center of gravity and potentially make it more challenging to control or recover from sudden maneuvers or road irregularities. Keeping the fuel level below the maximum capacity can help maintain the motorcycle's stability and reduce the risk of instability in certain situations.
Fuel Expansion: Fuel, particularly gasoline, can expand with changes in temperature. If the fuel tank is completely filled, there may be limited space for expansion, leading to potential fuel leakage or pressure build-up. Leaving some room for fuel expansion helps prevent any issues related to fuel expansion that could affect the fuel system or cause leakage.
Vapor Lock: Vapor lock is a phenomenon where fuel in the fuel lines or carburetor can vaporize due to excessive heat. A full tank of fuel can contribute to increased heat levels in the fuel system, potentially leading to vapor lock. By maintaining a fuel level below the maximum capacity, there is more space for fuel circulation and dissipation of heat, reducing the likelihood of vapor lock occurring.
It's important to note that the recommendations provided by the manufacturer are based on their engineering and design considerations. Following these suggestions can help ensure the motorcycle operates as intended and maintains optimal performance, safety, and reliability.