99 400ex rattling


my son has a 99 400 ex that he bought and ran fine for a while. the other day he was riding and it quit on him and couldnt get it to turn over again. all it did was just click at the seleniod by the battery. i think something locked up inside the motor. when he tried to push start it i think it un locked it and now it will start with the button but has a rattling sound coming from inside the engine. he says it has just as much power as before but the sound coming from the engine has me worried that something is broke in it. anyone care to take a guess as to what it might be that can cause this. im a 2 stroke guy as far as working on motors and i never been inside a 4 stroke...thanks in advance,Brian

My first guess would be a stretched timing chain. I would shut it down and check before riding it any further...

yeah i told him to leave it alone before more damage is done...i downloaded a service manual so i think im gonna try and tear into it the next couple days..wish me luck i never been in a 4 stroke so i dont know what to expect...lol

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