I bought a used 2011 yz250 that when purchased the PO handed me a set of rings and top end gasket kit. The bike had 100hrs on it and he said he planned to re-ring it 150hrs. I hadn't heard of "re-ringing" a bike, but at 150hrs the piston looked good so I stuck with the plan. I now have 200hrs and planned a for a full top end and not a second too soon!
Intake side
![ImageUploadedByThumper Talk1459125479.201848.jpg]()
Right side
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The cylinder will be sent to be replated. Note the scoring on the exhaust side
![ImageUploadedByThumper Talk1459125612.651261.jpg]()
Wear and no crosshatch anywhere else. This is intake side.
![ImageUploadedByThumper Talk1459125655.066346.jpg]()
The right side power slide (not sure what to call it, but its the little bullet like piece of metal that each of the power valve arms connect to) had gunk/sand stuck in it.
Only thing that makes sense is that during a wet/muddy enduro my pipe got bent away from the header. I finished the race and then swapped out to a back up exhaust for the second day. I'm guessing mud/sand/water might have gotten sucked up into the exhaust side? Not sure how else to explain exhaust side marring and sand/gunk in power valve? I always keep my filters super clean and the intake side isn't all that bad.
Anyways, one lucky find and I was a couple turns in last week's race from grenading the bike.
Top of piston...seems off. Lean? Pre-detonation? What's the fix. Go richer? Cool ace of spades though!!
![ImageUploadedByThumper Talk1459126353.152592.jpg]()
Spark plug. Was not wet..
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