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Discussion Starter #1
I'm overhauling my '95 Polaris XLT 600 engine and I was wondering about the allowed clearance between the piston pin and piston pin bore. My Clymer manual doesn't have that data, and I can't seem to find it anywhere.
When I stick the pin in one side of the piston and try to jiggle it, I don't feel any radial movement. But when the pin is fully inserted in the bore, it can turn without much resistance.
I measured the pin and bore and the clearance is between .001-.0015

I'm a Rotax aircraft engine mechanic and I work on both 2-strokes and 4-strokes. On the Rotax aircraft 2-strokes, the clearance wear limit is .002, yet I've never seen a pin that could turn as easily as those on my Polaris.

So is my tolerance still good?
Does anyone have the dimensions (new and wear limit) for pin diameter, pin bore diameter and pin/bore clearance for those Polaris pistons?

Thanks!
 

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i,ve never seen spec for that,but 001 cleareance,oil will take almost half of that,

myself ,i would put it together as is
 

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i just remembered the only way I got mine in was to leave the pin in the freezer for a half hour before I assembled it. Otherwise I couldn't get it in without lots of force. once frozen it slid right in
 

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Discussion Starter #4
On the Rotax's I use the same principle but I warm the piston with a heat gun instead.

My Polaris pins slide in rather easily at room temperature. Which prompts the allowable clearance question.
 

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i just put brand new pro x pistons in,and pushed the pins in with ease.no cooling,heating
 

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the circlip should hold them in, anyway. The reason why my motor needed a rebuild two years ago is cause the circlip left it's home, and the wall got all scored up.
 

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Discussion Starter #7
That's not what I'm worried about.
I'm worried about the pin turning too much in its bore while the engine is running (with the clearance increasing with piston dilatation), and causing accelerated excessive wear, then hitting up and down as it gets too loose, and eventually starting a crack and then... catastrophic piston failure.

Or maybe I'm just too uptight (pun intended) about all this.
A snowmobile engine isn't quite as critical as the aircraft engines I'm used to. [:p]
 
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