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MiranAdam16

2010 Yz450f cylinder/piston scarring after blown headgasket

4 posts in this topic

Recently my 10 450f started pissing coolant out of the overflow under heavy acceleration. We decided it must be a blown headgasket.

After tearing it down we noticed some pretty bad scarring on the piston and a little in the cylinder too.

What do you guys think could have caused this? I had just put a high flow water pump and new mishimoto radiators to resolve an overheating issue.

I guess it's big bored time, any kits you guys recommend? Any supporting mods recommended?

Thanks in advance for any info, Adam

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Edited by MiranAdam16

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That looks like classic piston seizure, in this case most likely as a result of the overheating condition causing a clearance problem or an oil failure.  

 

If you're going big bore, have the crank balanced for the new piston.  Use a two compression ring piston for best longevity. 

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Do you think the cylinder is worth using again with a stock replacement piston?

Edited by MiranAdam16

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Doesn't look like it.  But, if you can hone it clear of any scoring/marks and then measure it to be worn less than .002" anywhere, it could be. 

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