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.

  • When you open the throttle it prompts the ECU / injection system to add some fuel. The extra fuel is facilitating starting.
    – dlu
    Commented Nov 6, 2016 at 23:28
  • How hot is the engine when the issue occurs?
    – Zaid
    Commented Nov 7, 2016 at 11:28

1 Answer 1


As dlu pointed out in the comments the extra fuel is what is helping it start. but it could be several reasons why this is needed.

  • your injectors might be fouled
  • your fuel pressure might be low
  • it could be very cold out
  • you could have a lean or rich / flooding condition that needs adjusting
  • it could be a bad sensor causing the lean condition
  • it could be you have aftermarket cams tuned for a high RPM power band giving too much valve overlap
  • 1
    Good suggestions. I would also suggest checking the air filter(s) for blockage. Low airflow will cause issues too.
    – CharlieRB
    Commented Nov 7, 2016 at 15:04
  • @CharlieRB good point!
    – Cc Dd
    Commented Nov 7, 2016 at 21:00

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