The hole under the fuel tank of a Royal Enfield motorcycle serves a specific purpose. It is commonly referred to as the "vent hole" or "breather hole." Its primary function is to allow air to enter or exit the fuel tank as the fuel level changes due to consumption or expansion/contraction caused by temperature variations.
The vent hole prevents the formation of a vacuum or excessive pressure inside the fuel tank, which can affect the fuel flow to the engine. As fuel is consumed during riding, the air enters through this hole to replace the volume of fuel being used, ensuring a steady fuel supply to the engine.
Additionally, when the motorcycle is parked or stored, the vent hole allows air to enter or exit the tank as the fuel expands or contracts due to temperature changes. This prevents potential damage to the fuel tank, such as deformation or leakage, which could occur if the tank were fully sealed.
It's important to keep the vent hole clean and free from blockages to ensure proper air circulation. Regular maintenance and inspection of the vent hole are recommended to maintain the optimal performance of your Royal Enfield motorcycle.