How long should you hold the engine start button down?

Holding the engine start button down until you hear the engine start is the correct approach because this ensures that the starter motor has enough time to engage and cranking occurs through the engine system. When you hear the engine start, it indicates that the ignition system has successfully fired, and the engine is running properly.

If you release the start button too soon, the engine may not have had enough time to engage, which could lead to starting issues or a failure to start. Holding the button for just a few seconds allows for adequate engagement while not excessively stressing the starter motor.

The other options involve actions that either do not correlate directly to engine starting or rely on indicators that may not provide the necessary feedback. For instance, waiting for the fuel gauge to indicate full is not a relevant factor in engine starting. Additionally, until the lights turn on could refer more to bike readiness than engine start, and holding down the button without listening for the engine would not provide the confirmation needed for a successful start.