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Yamaha yzf can't start when overheat


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Hi everyone,

When i am trying to start my motorbike when engine is cold everything looks fine,

after few seconds when temp reach to 100 degrees Celsius (212 degrees Fahrenheit), i am turning off the engine.

now when trying to start it again engine wont start, please edvice.

video added.


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I haven’t had this bike before (I’m just going off mine) but have you got the choke turned on? That’s the only reason I can think of to why your bike won’t start. If the choke is turned on, the engine will obviously over heat.

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It depends what is actually happening.

When you try to start it when it is hot does it turn over at all, does it spin rapidly over or sluggishly, does it spin on and on and make no attempt to start, does it spin and try to start but fails and tries again to start and fails.

Cold starting needs more fuel than warm starting and warm running. The choke basically adds a load of fuel to the mixture so that the bike will start when cold in cold weather. If you leave the choke on and run a hot engine it will waste fuel. But if you try to start a hot engine with choke it usually doesn't start but floods and after flooding wont start at all.

If the mixture is very rich for some reason then this is the same as using choke.

Modern engines have sensors that tell the ecu to vary the mixture according to conditions and the state of the engine, and the yzf could well be one of those, the sensors tell the ecu how to behave and a faulty one could affect the mixture and then the starting.

I think more information about its behaviour is required before properly diagnosing this and a mechanic may be required if the engine/ecu is as complex as I suspect.

I would hope that a member who is more familiar than I am with the yzf might shed some light on this.

I am a little surprised that it only takes a few seconds to reach 100 degrees this doesn't sound right, I would have expected a few minutes, could this be part of the problem.

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I'd start simple, mate......could be that the starter motor is losing efficiency when it gets hot......or an electrical connection in the starter circuit that is going high resistance with temperature. .....doubt that it's your battery, but never rule it out...... 8-)

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Not sure if 100 deg Celsius is normal, my bikes didn’t get so hot in the middle of summer in Croatia where use to be almost 40 deg.

Maybe your cooling is not working and termo switch will not let it engine run or start if overhead.

Check cooling systems and termo switch

Fan should start at around 80 or 90 deg

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