YZ85 piston ring failure

YEM971
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YEM971
Edited Date/Time 11/9/2020 12:47pm
Has anyone seen a piston blow up like this?
Obviously the ring stuck on the exhaust port, I just don’t know why.
Any help/advice would be greatly appreciated.



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15tc150
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15tc150 9/29/2020 3:02pm
9/29/2020 3:02pm
Hooollllllyyyyy snotsicles! That is EPIC! The only thing I could gather from that, is the possibility that your ring locating pin came loose and your ring walked around the piston to the exhaust port, but that’s extremely far fetched, or your ring snapped in two, but both of those are probably wrong, but it’s strange that it didn’t affect the Center of the piston in the breakage, the cylinder looks like it can be salvaged though, so not a total write off, At least that’s somewhat of a silver lining
Falcon
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Falcon 9/29/2020 4:00pm
9/29/2020 4:00pm
How many hours on the ring? I can imagine a worn ring moving off the locator pin or moving around into the ports, but I can't imagine it still having enough compression to run. I have seen that same seizure before, though.
DynoDan22
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DynoDan22 9/29/2020 4:46pm
9/29/2020 4:46pm
Ring land pin ejected and the ring spun. The open end of the ring caught the exhaust port. Look very closely in the first pic and you can see the witness mark of the ring end that smashed into the piston. The only way that can happen is if the ring land pin come out and it allows the ring to rotate. Wiseco had an issue with that a while back.
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slipdog
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slipdog 9/29/2020 5:17pm
9/29/2020 5:17pm
DynoDan22 wrote:
Ring land pin ejected and the ring spun. The open end of the ring caught the exhaust port. Look very closely in the first pic and...
Ring land pin ejected and the ring spun. The open end of the ring caught the exhaust port. Look very closely in the first pic and you can see the witness mark of the ring end that smashed into the piston. The only way that can happen is if the ring land pin come out and it allows the ring to rotate. Wiseco had an issue with that a while back.
Good eye!

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DynoDan22
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DynoDan22 9/29/2020 5:47pm
9/29/2020 5:47pm
Yep. You can see a perfect indentation of the ring end in the piston. Mystery solved.
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sandman768
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sandman768 9/29/2020 6:50pm
9/29/2020 6:50pm
15tc150 wrote:
Hooollllllyyyyy snotsicles! That is EPIC! The only thing I could gather from that, is the possibility that your ring locating pin came loose and your ring...
Hooollllllyyyyy snotsicles! That is EPIC! The only thing I could gather from that, is the possibility that your ring locating pin came loose and your ring walked around the piston to the exhaust port, but that’s extremely far fetched, or your ring snapped in two, but both of those are probably wrong, but it’s strange that it didn’t affect the Center of the piston in the breakage, the cylinder looks like it can be salvaged though, so not a total write off, At least that’s somewhat of a silver lining
That cylinder looks hammered!
15tc150
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15tc150 9/29/2020 7:15pm
9/29/2020 7:15pm
15tc150 wrote:
Hooollllllyyyyy snotsicles! That is EPIC! The only thing I could gather from that, is the possibility that your ring locating pin came loose and your ring...
Hooollllllyyyyy snotsicles! That is EPIC! The only thing I could gather from that, is the possibility that your ring locating pin came loose and your ring walked around the piston to the exhaust port, but that’s extremely far fetched, or your ring snapped in two, but both of those are probably wrong, but it’s strange that it didn’t affect the Center of the piston in the breakage, the cylinder looks like it can be salvaged though, so not a total write off, At least that’s somewhat of a silver lining
sandman768 wrote:
That cylinder looks hammered!
You should have seen my 144sx cylinder after the wrist pin c clip warped and got dragged beside the piston, there was a 2mm groove dug into the side of the cylinder, I thought she was a write off, that cylinders on its 2nd replate now, and can’t even tell anything had ever happened, that 85 cylinder isnt much worse, I was extremely surprised when I was told it would run again, but it lives!!! Hahahahaha
450
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450 11/9/2020 12:47pm
11/9/2020 12:47pm
Just had the exact same thing happen on our 19 yz85. On ours the locating pin for the ring came out of the piston and allowed the ring to spin. Anyone here have any theories on what could cause the pin to come out? This had just over 11 hours on the piston. Thinking maybe expansion rate from warming up?

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