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piston read please.

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I,m lucky if I get 10 hrs out of me kids 10 yz85 piston rings. On some of our previous yz 85s I would go 25 to 30 hrs on a piston and ring no problem. Mid pack nov rider, bike is running 32.1 on 91 pump with a nice golden brown plug. Any suggestions? looks like it might have gone a little lean.

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Just my 2 cents. Looks like the ring was not sealing well. Shouldn't see so much dark oil burn below the ring.

Were you able to confirm the piston to cylinder wall clearance, when it was fresh? May have been to loose initially.

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it's apart, change it    looks like it's running fine but pics don't show much.  Polished spot 1/2 way up the skirt is only suspect thing I see

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Ron, I did not check piston to cylinder wall clearance and i,m sure running a b piston in this high hr cylinder was not the best choice. Highmarker , It is definitely getting new parts, I was not trying to reuse them. Thanks for the reply's

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Almost looks like you may have head oring just seeping a tiny bit it's pretty black.  Pic below is same bike just way worse.  And it still would start 

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Before ordering a piston, you should have measured the cylinder for out-of-round, taper and bore diameter (worn plating).

If any are out of tolerance, no matter the tighter fitting D piston, it will still continue to wear in the same fashion as your previous piston(s) did.

Edited by mlatour
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