The sound you hear when switching on the ignition of your Yamaha FZ-S Version 3.0 could be the normal sound of the fuel pump priming. Fuel-injected motorcycles like the FZ-S Version 3.0 have an electric fuel pump that pressurizes the fuel system before starting the engine. This priming sound is typically a brief humming or buzzing noise and is a normal part of the startup process.
If the sound is a continuous or abnormal noise, it could indicate a potential issue with the fuel pump or another component in the electrical system. In such cases, it is recommended to have your bike inspected by a qualified Yamaha technician or a trusted mechanic to diagnose and address any potential problems.
It's important to note that without a physical inspection, it can be challenging to determine the exact cause of the sound. If you have concerns or if the sound is accompanied by other abnormal behavior or warning lights, it's best to seek professional assistance for a proper diagnosis.