Reading a piston

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Lemming

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• Jul 25, 2002

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I just did a topend job on my '99EC200. Below is a photo of the piston. My take on the read is that all looks well, but I'd like to hear from the experts.

History, this is the original piston and it has 1.75 years of use. New rings were installed about 6 months ago during a bottomend rebuild. At that time it was deemed that the piston was still looking good but should be replaced when I did the topend by midsummer.

 

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• ec200 piston.jpg

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bwalker

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• Jul 25, 2002

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Lemming it looks like the piston may have been running on the cool side suggesting that your jetting is rich.

 

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Lemming

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Well there's no doubt that I tend to err on the rich side with my jetting.

 

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Durt Cycler

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Kinda looks like the jetting was pretty good for almost 2 years on it.

 

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Shift-MX

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• Jul 25, 2002

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well the jetting was for sure ritch...hence the carbon build up on the top of the piston...what does the side look like?

 

MoO_coW

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• Jul 26, 2002

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How about the underside?

 

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Lemming

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Ask and ye shall receive :silly:

 

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Lemming

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Side view.

 

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bwalker

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well the jetting was for sure ritch...hence the carbon build up on the top of the piston...what does the side look like?

Click to expand...

You guys havent aclue what you are talking about. The carbon builds up from heat. A bare piston with a small spot underneath the plug indicates it is way rich. A motor that is jetted close will have a piston that has a light brown carbon pattern over the entire dome with the exception of a few thumb nail size spots where the tranfers enter at.

 

WoodsRider

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• Jul 26, 2002

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Lemming - It looks good to me, but then I've spent the week looking at locomotive pistons that are in pieces. :scream:

You should have seen the one I pulled out of my EC250 after overheating at a hare scramble last April. After 1.75 years it's time to measure/hone the cylinder and install a new piston kit.

---Woods

 

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fatty_k

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• Jul 26, 2002

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This should help you guys out:

http://www.ericgorr.com/twostktech/pistondiaguide_2t.html

As long as the underside isn't black (way lean, which it isn't) I think you are in good shape.

 

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Lemming

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Ben, is the reason for the diagnosis of running rich due to the rather large "bare" spots around the perimeter?

Woodsy - the new piston kit was in before the photo was taken. I just wanted to get a read to see if, in general, my jetting was ok.

 

bwalker

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Yes.