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Pistons - What size?

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Hey guys - quick question that I am sure someone has the answer to....

How do you tell the size of a piston? For example - I bought a used CR80. The guy I bought it from said that it had been bored .20 over. He sent the head out.

I am thinking that he had the cylinder re-sleeved, not oversized, as I cannot find a piston that is oversized for that model. :)

If I pull the head off and take the piston out, is there a way to tell on the piston what size it is? I know that there are numbers and markings on the piston, I just don't know what they mean.

The bike is running ok, but seems down on compression, and is blowing black "spooge" out the head. My spark plug is a nice golden brown.

To me this says that it needs a top end, or at the very least rings.

Whadda ya think?

Thanks

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Pull the cylinder, measure the bore size -- see if it is OEM size or over bore. If it is bored out bigger you will need to get the right piston to fit it. In your case it would be a 20 over piston. (I think that means 0.020" oversize) I'm sure wiseco sells them...

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if it has black stuff coming outa the head then head gaskets would help alot... but if your that far atleast put rings in it

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