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1995 Polaris Sportsman 400 Compression


bren7176

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Was that a 2 stroke? Can't remember. I would assume fresh rings and good seating would be more like 150 psi, I would think 100 PSI would be about the low end.  I had a 4 stroke Bayou 220 that ran like a champ with 80 psi but that's a 4 stroke....

If compression is at 90 I'd think that's about low enough to keep it from sucking fuel in and running right...if running at all.

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ya its a 2 stroke ,  Well took it apart and the jug looks bit beat up and the piston is not so good looky .. all scratched and and ruff .. looks like it was run with bad mix..  well it did sit at a hunting camp for over 20 years in a garage  not being used . sad thing ,  has less then 500 miles on it . time for a top end rebuild .

 

 

 

IMG_9384.thumb.JPG.2d9d469c42a0326759eadf1c9a9263f1.JPG

Edited by bren7176
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That scaring on the skirt doesn't look that bad as the rings look pretty smooth.  If the cylinder wall isn't toast a quick refresh with a hone and some new good rings and i bet it runs like a champ.  I'd probably even buff out the piston skirt and reuse since OEM is always better than repop.  The scratches may just be years of sitting and then the carbon deposits flaking off when trying to fire it.  I've seen worse run. :)

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Point taken @Frank Angerano.  The reason I was thinking recycle the piston is that the skirt never touches anything, it's just there to let oil pass to the rings.  Hell, if the skirt touched anything it would be tragic!  But with pistons, even Wiseco, not really being that big of an investment...it's probably better safe than sorry.

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