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HELP! 450 dead. Not starting

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Friend was riding my sm450r and didn't even finish a full lap. From what he was telling me, he may have over revved. Checking spark plug, reveals there is no more plug gap! Regapped plug, and still does not start... Appears piston is still hitting the spark plug. How common is this and what does it sound like the problem is? Valves were adjusted & new oil 2 days prior... Haven't been riding too hard.

Has this happened to anyone before? Engine cranks over but does not start. Looks like its hitting even when I just try to start it (electric). Ideas? Thanks in advance

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You might have snapped a valve head off.

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You might have snapped a valve head off.

Almost for certain!

Is this an 04?

I have one 04 in the shop right now that we are waiting on parts but plan to upgrade to the 04 parts (bigger stems), I have done three with the Hall steel valves.

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Yes 04... Any way to tell by lifting the valve cover? Took a look and springs/valve guides looked in tact and moved as they should when crank is turned. Another thing is clutch doesn't seem to be engaging. When in gear and clutch lever pulled, bike will not move. Or is this just bcuz engine is cold? Thanks again fellas

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something slammed into the plug--most likely that was a valve head.

stop trying to start it.

time to pull the head--or even just pull the plug and get a flashlight and look down there-you might see the head...you can handcrank the motor but not if theres any resistance....

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do you know what happens to cause this? why it would all of a sudden cause the valve to drop? could it have been an error in the valve adjustment? it was running fine for 2 20minute sessions, then on the next outing didn't even get through turn 5 (10turn track).

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In 2004, Husqvarna had issues with some valves which is why they increased the stems and changed suppliers for 2005. Probably a manufacturing flaw, poor heat treatment, material, etc.

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