Polaris ATV Forum banner

1 - 6 of 6 Posts

·
Registered
Joined
·
57 Posts
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
 

·
Registered
Joined
·
2,885 Posts
Measure it. Are you just doing a hone and re-ring on it?
 

·
Registered
Joined
·
5,753 Posts
Need to measure the bore, the piston, and remove the rings and put them in the cylinder to measure end gap. That will give you what you need to know to order the correct parts.
 

·
Registered
Joined
·
57 Posts
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
 

·
Registered
Joined
·
5,753 Posts
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.
 

·
Registered
Joined
·
57 Posts
Discussion Starter #6
yes wont fit in grooves so I am sending them back and how long does a rebuild last b4 u have to rebuild it again
 
1 - 6 of 6 Posts
Top