This is a question about a motorcycle engine (specifically a Yamaha FZ6 2011, which has electronic fuel injection). Occasionally this happens when I try and turn on the bike: I will press the starter, and the engine turns over, making that characteristic "crackling" sound.
Usually, the engine will ignite after a few "crackles". Sometimes though, it just seems to crank onwards. However if I twist (open) the throttle during this process, the engine starts.
It is not a battery problem as the battery was recently replaced. I believe the spark plugs are due for replacement soon (according to the service manual), but I'm not sure I understand why opening the throttle would make any sort of difference to the starting process.
This doesn't happen all the time. I'd say 80% of the time, the bike starts off normally without me touching the throttle.