Piston look normal??

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10/14/2018 11:46 AM

This is my kx80, has probably 15 minutes on it. I bought a used rebuilt bottom end and had cylinder replated and fresh piston and rings. Got it out this morning to ride and started up fine and then stalled out while idling. Kickstarter wont move and this is what piston and cylinder look like. cylinder feels good and smooth. Photo
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"So you're telling me there's a chance!!"

10/14/2018 11:52 AM

Photo
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"So you're telling me there's a chance!!"

10/14/2018 1:31 PM

No thats not normal at all. Its got scoring on the sides. Exactly why that is, im not really sure. Maybe check your piston to cylinder clearance, and ring gap.

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10/14/2018 1:35 PM

Would that cause bottom end to lock up? I pulled clutch out and the shaft coming out with gear on it, that appears to be crank wont move.....

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"So you're telling me there's a chance!!"

10/14/2018 1:51 PM

Bad bearings, a circlip from the piston that came out, metal pieces, etc... split your cases and find out. That crank looks dirty. Im not sold on the bottom end rebuild they did.

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10/14/2018 3:04 PM

yeah, i worried about the bottom since I bought it complete, but the top I did myself with all new parts so I'm at a loss I guess on the piston scoring. 15 minutes on a newly replated top end. I guess I need to buy a case splitter now, dang it what a day

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"So you're telling me there's a chance!!"

10/14/2018 4:00 PM
Edited Date/Time: 10/14/2018 4:00 PM

Live and learn man. It could have been a lot worse. I had a yz250 that blew up on me within 1 hour of owning it and it damaged a ton. Definitely sucked.

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10/14/2018 9:02 PM

I do not know if it is just the angle of your pictures.... but it looks like your crank is NOT centered in the cases.
You should always center the crank in the cases before assembling the top end.
This could be the reason why the bottom end is tight.
If possible make sure the main bearing are also seated correctly.
Hope this helps.

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10/19/2018 8:31 AM

that cylinder looks like total crap for being replated and only having 15 minutes on it.

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10/19/2018 10:35 AM

Ti wrote:

I do not know if it is just the angle of your pictures.... but it looks like your crank is NOT centered in the cases.
You ...more

Yeah, It looks like left side is jammed against case. That crank doesn't look new either but maybe rebuilt with new rod?
Piston looks like possibly ran with straight gas vs mix or pulled air through LH crank seal?............

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10/19/2018 7:48 PM

Wiseco piston ? Does it have the lube holes drilled in it on the exhaust side of the skirt ? The exhaust port bridge on the cylinder looks scuffed pretty good. Clearance was set proper ?

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