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  1. #1

    Question Rebuilding only one Cylinder/Piston?

    I rebuilt the entire top end of my Polaris SLT 780 last spring, but by the end of the summer the middle cylinder was burned on the edge this time. My assumption this time is that some junk from the bottom of the gas tank that was not fully cleaned out plugged up the center carb resulting in running lean. The other two pistons are in perfect condition. I was searching the forums and couldn't find what I was looking for. I am going to completely clean the fuel tank and get all new fuel lines and rebuild the carbs, but is it okay to only rebuild that center cylinder this time? Any help would be appreciated. Thanks!


  2. #2
    What was the compression on the other 2 was it in spec?

  3. #3
    Quote Originally Posted by Robfromga View Post
    What was the compression on the other 2 was it in spec?
    A local shop tested it before taking off the cylinder heads, but all they could tell me when I picked it up was there was no compression in the center cylinder. I could put them back on to test it myself, but since the gaskets have been separated I don't know if it would be accurate.

  4. #4
    Quote Originally Posted by Robfromga View Post
    What was the compression on the other 2 was it in spec?
    From looking at the piston heads, the other two appear to be just fine, like when I put them in last year. However, the Middle one, with what I know had no compression, will wiggle and is burned up on the Exhaust side. Assuming they are both in spec as far as compression goes, Would a single piston rebuild work and set the rings properly and everything?

  5. #5
    Depends on the hours if its worth it or not. Im, literally doing the same thing on a 8 hour old build. Ring split on a piston. Nothing got into the bottom end.

    If the other 2 are within spec and money is tight I'd go for it. Others may disagree. Are you sure nothing got into the bottom end?

  6. #6
    Quote Originally Posted by Robfromga View Post
    Depends on the hours if its worth it or not. Im, literally doing the same thing on a 8 hour old build. Ring split on a piston. Nothing got into the bottom end.

    If the other 2 are within spec and money is tight I'd go for it. Others may disagree. Are you sure nothing got into the bottom end?
    It would definitely be easier financially to only rebuild one, but if its going to cause more problems aka more money, I would rather do them all. And I have not taken the cylinder out yet, So I am really unsure about that. It is burnt up less than last time and I had nothing in the bottom end before so I would like to think I would be ok now. How should I go about checking for debris in the bottom end? Just physical examination from the openings?

  7. #7
    & The build from last Spring has less than 20 hours on it for sure.

  8. #8
    If something came apart, like chunks of the piston, I'd say that there's metal floating around someplace. Its always cheaper to rebuild it now right, than chance it and have a catastrophic failure. If there's any chance of junk in the bottom end I'd rebuild the whole thing.

  9. #9
    Sooo...how much for the 780? stimpsonjcat's Avatar
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    Yep, I have done this twice now with good results.
    PTO on one ski, and MAG on the recent one.

    As long as nothing has gotten loose in the cases you should be fine.

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