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Discussion Starter · #1 · (Edited)
OK I'm going to put new rings in my 350 trail boss motor while I have the head off so how do I tell if piston is stock there r no markings on the piston its smooth no numbers letter or anything and I'm pretty sure its stock but I want to make sure its not bored out and I order the wrong rings
 

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Discussion Starter · #4 ·
I got it I looked at stock piston on eBay and it was like mine so I went off that and by the way don't buy a namura (std) piston they r thicker they won't fit in the groves they r the correct size not thickness but thxs
 

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What do you mean the Namura won't fit in the grooves? I've used dozens of them without issues on different machines. Are you talking about the rings not fitting the piston grooves? They have a keystone shape and only fit one way. If you put them on upside down they won't go into the grooves. There are specs that the piston to cylinder wall clearance and ring end gap need to be for it to run right and be reliable. To much cylinder to piston gap and you will break off a piston skirt and score up the cylinder. To much ring gap and you will have low compression. To tight on either and you can stick a piston or break a ring. We're talking the difference of .003" total here.
 
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