I have a question regarding my motorcycle (Yamaha FZ8 - 4Zylinder 800cc). At the weeksend I was driving through a town. It was very hot outside and I parked the bike. The coolingwater-temperature was above 100°C, the fan of the engine was running.

When I turned of the engine, the fan stopped working, too. So I switched on the ignition again (without starting the engine), and the fan started working again. After a few minutes I turned off the ignition, because the fan was still runing and didn't want to risk to loose all the battery power.

My question is: What is the correct way in such a case? (Hot summer temperatures + hot engine)

  • Leave the eninge turned on? Will it cool down, or will the engine produce more heat, than it can cool down? (For some turbo cars, it is best in this case, to let them running, but for motorcycles?)
  • Let the vent running(without the engine)? How long does the battery last, if I let the ignition turned on?
  • Just stop the engine and don't care if it's hot? (Will it take damage?)

Hope you guys can give me a hint.

Best regards.

2 Answers 2


Stopping a naturally aspirated engine will cool it down, regardless of the fan running and etc. The idea behind "turbo timers" on turbocharged cars is not at all engine cooling related, rather it is to allow the delicate and extremely hot turbocharger components to cool down via keeping the oil feed circulating through it for additional 15-30 seconds or a minute. I think it's totally OK to stop your bike without worrying about the fan.


Also I want to add my 2 cents. When I look at Yamah FZ8 I see that it is water cooled... so I think that the purpose of the fan is to push air on the cooler as it should have a bigger surface than the engine itself. When you turn on the ignition the fan pushes air on the cooler but the water pump is not running as the engine does not run. So I would think that running the fan - without establishing water circulation - will have a small impact.. Correct me if I am wrong.

If you are afraid that the engine could take damage on hot days. Briefly before shutting down the engine, the best way is to drive relatively fast (watch the speed limit) with the highest possible gear and low revs.. that way a lot of air can hit the cooler unit while the water pump is running and the low revs will create relatively low temperature. This should cool down the engine

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