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joradn_schmit

03 Yz450 issues. Got any ideas?

11 posts in this topic

i recently bought a 2003 yz450. It is a killer bike, but last weekend i was riding and the engine shut off while the throttle was wide open. Now it wont start at all. I changed the plug and that didnt help. Anyother option of what might be wrong?

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i recently bought a 2003 yz450. It is a killer bike, but last weekend i was riding and the engine shut off while the throttle was wide open. Now it wont start at all. I changed the plug and that didnt help. Anyother option of what might be wrong?

"Guns don't kill people, the government kills people." -Dale Gribble

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Did it just quit like you hit the kill switch, or sputter and die? If it just quit like the kill, I'd personally go through all the electrical connections starting with the kill switch and look for disconnected wires. Theres no telling what the previous onwer did to it, like possibly a heavier flywheel or something that compromised the wires in the ignition coil.

If it sputtered, start with the carb and make sure everything is in order. a stuck float or some other simple condition could be the culprit.

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When it shut off, did you just roll to a stop? No locking up or bad noises(grinding, popping?)? If so, I would think there is something wrong with the ignition. How about changing the plug first, and then checking all the contacts?

If you lost fuel, there would be some popping, like when you forget to turn the fuel on and ride a bit. If there was anything mechanically wrong (valvetrain or crank/piston) there would probably have been noises and the engine would feel weird even when kicking it over.

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i'm pretty sure i narrowed it down to something with the carb. I just have to figure out what the issue is. What would be the easiest way to start checking? Any ideas would be greatly appreciated.

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I guess you could be running out of fuel, so check that your floats and needle valve work. They usually get stuck in the open position though, so you get fuel overflow from the carb. Also, pull out your idle jet and make sure it's not clogged. Could be a bit of water in there as well. Check the plate that is on the cylinder side of the carb slide.

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The old rule spark fuel or air. Air is fine cause it was running. Fuel its self should be ok as it was running. My guess is spark or terminal failure in valve or timing train somewhere. You said you changed the plug, but did you check the plug had spark and was it good spark.

A quick check for the carbie is to turn the bowl drain screw as the float may have become stuck up and run dry. Un likely but may cause the problem you described. Do a compression test if you can access one, to save you pulling the engine down to look for some of the obvious causes.

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Have you pulled the carb completely off the bike and looked to see if a jet came loose, ie the main jet backed out and fell to the bottom of the float bowl?

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