2005 YZ250, son overheated it. Opinons, advice?

kzizok
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kzizok
Edited Date/Time 4/25/2017 3:09pm
I told him to make sure fluids, etc were topped off but he didnt. I had put new top end etc., so told him to double check everything before, during, and after as I wouldnt be with him. So, it overheated, compression was down. Never seized. Following are pics. My questions are, does it need a new head? Head nuts were loose when I went to take it off too. Cylinder was new, and still looks good but does it need re-done? Piston looks scorched (which was new). What do you guys think?











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Falcon
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Falcon 4/24/2017 3:02pm
4/24/2017 3:02pm
Stuff warps when it gets hot. I'd surface the head, for sure, at the very least. You may want to remove the studs and do the same to the cylinder on both ends as well.
The good news is that 2-strokes are a simple heat pump and there's not a lot of moving parts that could have gotten ruined. Check your bearings for excess play

Better mechanics than I will likely chime in with some advice soon. Guys??
pete24
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pete24 4/24/2017 4:16pm
4/24/2017 4:16pm
on the top left of your head pic can you see the side of the combustion chamber, that looks ragged? thats detonation and that head needs to be surfaced till that is cleaned up and the chamber re cut, you need to look at the cylinder as well around the outter edge and see it that has it as well, your best bet is to send that stuff ti millenuim for inspection and repair
kzizok
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kzizok 4/25/2017 6:53am
4/25/2017 6:53am Edited Date/Time 4/25/2017 6:54am
pete24 wrote:
on the top left of your head pic can you see the side of the combustion chamber, that looks ragged? thats detonation and that head needs...
on the top left of your head pic can you see the side of the combustion chamber, that looks ragged? thats detonation and that head needs to be surfaced till that is cleaned up and the chamber re cut, you need to look at the cylinder as well around the outter edge and see it that has it as well, your best bet is to send that stuff ti millenuim for inspection and repair
Pretty much what I was thinking. Thanks, Pete and Falcon

Kind of thought I would get more than two replies.
Dtat720
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Dtat720 4/25/2017 8:00am
4/25/2017 8:00am
I'd be willing to bet that detonation on the head lines up with the spot on the piston, most likely that apot on the cylinder will be pitted as well. The spot on the piston in the pic is at the bottom and looks like a line coming off the edge, you can see it softened(melted). Decking and checking the bore for out of round is for sure the first step

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Eddie_E
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Eddie_E 4/25/2017 12:44pm
4/25/2017 12:44pm
kzizok wrote:
Pretty much what I was thinking. Thanks, Pete and Falcon

Kind of thought I would get more than two replies.
Sometimes two really good posts are better than a hundred half assed posts. This is one of those times.
Some pictures of boobs or Ronnie Mac passed out with a can of PBR always adds entertainment though.
kzizok
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kzizok 4/25/2017 3:09pm
4/25/2017 3:09pm Edited Date/Time 4/25/2017 3:09pm
kzizok wrote:
Pretty much what I was thinking. Thanks, Pete and Falcon

Kind of thought I would get more than two replies.
Eddie_E wrote:
Sometimes two really good posts are better than a hundred half assed posts. This is one of those times. Some pictures of boobs or Ronnie Mac...
Sometimes two really good posts are better than a hundred half assed posts. This is one of those times.
Some pictures of boobs or Ronnie Mac passed out with a can of PBR always adds entertainment though.
Good point. Im just gonna send them to millennium.
Acidreamer
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Acidreamer 4/26/2017 6:14am
4/26/2017 6:14am
You need to check for warpage on all of the mating faces. Where your cylinder meets the cases, and where the head meets the cylinder. If its not perfectly flat you need to replace it all. You might be able to have it machined flat, but i wouldnt trust it.

Next time double check his work and watch him like a hawk. I have to do the same thing to my younger brother and youd be surprised at some of the goofy shit i find.
Skerby
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Skerby 4/26/2017 8:00am
4/26/2017 8:00am
I ran my YZ out of water, bad base gasket, It was a fresh top end like yours. Ran the piss out of that thing until it started to sound weird, touched the radiator and was confused as to why it wasn't hot, oh shit lol. Anyways I just threw in a new piston and all was well.

Mine got hot enough to melt the clutch cable.
Paw Paw 271
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Paw Paw 271 4/26/2017 4:17pm
4/26/2017 4:17pm
Get a new son or start letting him pay for the fix's.
Get you r cylinder checked for size and shape and go from there.

Paw Paw

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