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What is my piston telling me?

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I need some assistance in understanding what the different colors on the piston is telling me.

 

As you can see in the pictures below the top side edges of the piston are a lot darker over top of the wrist pin areas on both sided compared to the the other. Does this indicate a condition of the cylinder, rings, etc.? Trying to figure out if the piston is still good or if a new one is needed.

 

Any thoughts on your experiences is helpful.

 

 

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I need some assistance in understanding what the different colors on the piston is telling me.

 

As you can see in the pictures below the top side edges of the piston are a lot darker over top of the wrist pin areas on both sided compared to the the other. Does this indicate a condition of the cylinder, rings, etc.? Trying to figure out if the piston is still good or if a new one is needed.

 

Any thoughts on your experiences is helpful.

 

How many hours are on it? If you don't know, then I would replace it. I personally don't open the top end and pull a piston out... and then put it back in. They are cheap enough and I am already in there, so I replace them. 

 

I'm on my phone so it's hard to see, but that appears to be more carbon than I usually get and some blow by on the first ring. Hard to see it though. 

 

This may help you out;

 

http://www.smellofdeath.com/lloydy/piston_diag_guide.htm

Edited by Kenpo1
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Pistons wear front and rear more than side to side. Thats what youre seeing.

 

You can measure it up but it appears to have quite a bit of wear. Replacement time.

 

Looks like shes been in there a while. TTR125 ridden in the sand?  BOOYAH

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Some of the pictures in that link may give me nightmares....  :smashpc:

 

There does look to be a little blow by on the first ring, as pointed out. Good time to change the piston and be sure you're gapping the rings carefully. I would worry too much as long as the cylinder looks healthy, bottom of the piston looks ok

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Thanks for the responses, would this be an indication that the cylinder is oblonged now as well? This came out of a 2001 and assume it is the original parts.

 

I am thinking I should have the cylinder bored over with new piston/rings. I was trying to use this as a learning opportunity to be able to tell what is going on visually by looking at the parts.

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Thanks for the responses, would this be an indication that the cylinder is oblonged now as well? This came out of a 2001 and assume it is the original parts.

 

I am thinking I should have the cylinder bored over with new piston/rings. I was trying to use this as a learning opportunity to be able to tell what is going on visually by looking at the parts.

 

Well, there is no scoring or excessive wear on the piston, so it's hard to say what your cylinder needs. Truth is, you really ought to stick a bore gauge in there (or take it to a machine shop) and get an accurate measurement. 

 

Otherwise, get some good pictures of the inside of the cylinder, ports, exhaust valve and post them. That way we can at least look for cross-hatching etc for some indication. 

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What year and model bike with a plated cylinder is being discussed?

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The top ring isn't sealing, the bottom two are ok.

Like Kenpo1 said, replace those cheap pistons while the bike is apart. Your recreational time is valuable, and you would hate to plan a big event and have a mechanical failure when you can solve the problem now.

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