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Discussion Starter · #1 ·
I'm totally stumped. My 03 400ex will start up no problem when it's cool. I can ride it till it reaches normal operating temp then it shuts off, when I try to start it back up it acts like battery is dead but, after it dies and I let it cool down for 2-3 mins it fires up no problem. Once it gets hot again it does the same thing.

Any help is greatly appreciated.

Motor all stock, white brother e series slip on, yfz 450 carb, jetted properly, brand new battery, and other bolt on's. Someone please help.
 

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OK - let's start over

Cranking is the when you are trying to start it and the engine is "cranking" (same as turning over) - I presume when it dies, it will crank but is not starting

Not starting - you have to determine which part of the formula is wrong - the formula is: if you have sufficient compression, spark, spark at the right time, fuel and air in the right amounts, it will run

Try to determine if you have lost spark - carry an extra spark plug - when the engine dies, pull the plug cap off, stick the extra plug into cap, touch the base of the plug to the engine and crank the engine - if you have spark, then you have to check the other parts of the formula

Note: coils seldom go bad - losing spark when hot and getting it back again when cool many times can be a poor connection somewhere or a short in the kill wire - the ignition is cut when the black wire with the white stripe is grounded.
 

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Discussion Starter · #6 ·
Ok thank you I know it has spark, as far as when it gets hot it acts like the battery is dead and it won't crank over. But compression is good, I'll check out the black wire with white strip and follow it back and make sure there are no bars spots
 

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This is good information - now I am leaning towards a charging system system problem since you say it acts like the battery is dead. Usually if the solenoid just clicks, it is a dead battery, but if the engine is tight for some reason and extra hard to turn the crankshaft, it can act the same way.

Try push starting it when cold (you will need a helper to push) - when it gets hot and dies, try pushing starting it again and see if the engine spins over normally or if it seems tight. If normal, try jumping the battery with another battery or booster pac.

Let me know what you find out
 

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Discussion Starter · #10 ·
I tried to jump the starter itself with another battery and it just clicked, I took the cover off and took the gears out and tried it again and the starter spins freely. I'm confused on this now my bike will not even turn over. Gonna try and take plug out tomorrow and roll over by hand and check spark, if I have spark I'm gonna try and bump start it.

Last time I buy something from some young kid
 

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Discussion Starter · #11 ·
Its like the gear isn't making contact with the engine gear sorry for poor terminology not to sure on what it's called. Not sure if I have a bad one way bearing now or what the deal is.

Hopefully it bump starts. Any suggestions on bumping it as far as what gear to try it in?
 

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Push it in neutral till up to speed and without using the clutch, just click it in to 2nd gear

Since you just posted what you did, if you have a bad one way clutch, the solenoid will click, the starter motor will whirr, but the motor just doesn't crank. Should have nothing to do with just dying suddenly
 

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Are you certain the motor is stock? And by stock, do you mean original or rebuilt to stock specs? If it dies when it gets hot and won't crank even with a good battery, but it starts fine when cold, it sounds to me like some internal part could be expanding when hot and binding up. If the rings are not gapped properly they could be expanding too far and locking up the piston. Try turning the motor over with a wrench manually on the crank when cold, then run it until the problem shows up. Then try turning the engine over manually again while still hot and see if it is in a bind.
 
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