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  1. #1

    1995 Polaris SLT 750 - burned middle piston

    After fixing my SLT 750 (new cdi, fixed MFD, triple fuel pump installed) - it was running well until this weekend.

    The middle piston has burned a hole - cannot figure why this happened. This thing is premix 32:1, and was running perfect until this happened.

    I can only think that the new fuel pump is not pumping well (due to bad reed valves?) - as this thing just stopped once over the weekend after having it full throttle for about 3 minutes continuous. After that happened, it just started right up and went on for another 3 hours running.

    I don't know what to do at this point. Anyone out there have a good, cheap piston for this thing? I love this ski - but it's adding up to the point where I am getting scared off.


  2. #2
    BlueFishCrisis's Avatar
    Join Date
    Aug 2011
    Medina, Ohio, United States
    Welcome to the Hulk!!

    Got any pics of the fried piston? How about all three while we are at it?

  3. #3
    No pictures yet - just winterized the ski and pulled the battery.

    Looking at the top of the piston through the spark plug opening- It does not look like it was running lean. It's dark with carbon deposits on the surface of the piston - but that could mean anything (could have been starved for fuel on an acute event).

    I'll get some pictures when I get into it up on this site...

    Has anyone installed an electric fuel pump on these skis? I think that I will go that route if I decide to fix it up - depending if I can get parts without taking out a loan...

  4. #4
    And thanks for the welcome! I look forward to posting here in the future.

  5. #5
    bowsniper's Avatar
    Join Date
    Aug 2008
    Sounds like you "stuck" a piston for a second. When you ran it full throttle for those 3 mins, was it warmed up? the bores need time to expand to the piston.

    a reason for getting a hole in a piston is because it went lean. when you take the head off, if the piston is all dark on top, thats real lean. clean spots on the piston near the ports is what your want to see. a totally clean piston can indicate a spark problem or your way rich.

    check the bore and see if its scored. look at the ports and look for chips missing.if the piston and rings are intact, you may be able to get away with a piston and some rings, and a light honing.
    you still need to find out why it happened or else it will happen again.

    air leaks, a plugged line or carb, needle n seat stuck closed,bad ring gapping are a few to consider. any maintenence done to the motor at all? carb rebuilds?

    what routing diagram did you use to do your triple outlet pump? from here? was this the first time out after the rerouting? just wondering.. I cant see your ski,

    Welcome to the Hulk...

  6. #6
    Banned User
    Join Date
    Jun 2010
    Milwaukee WI
    Did you ever clean/rebuild the carbs?

  7. #7
    MSRXP's Avatar
    Join Date
    Sep 2010
    Central MS
    Please post a picture when you get a second.... Also, a picture of the plug as well.....

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