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  1. #1

    2003 polaris msx 140 center cylinder melt down

    good evening. i just picked a 2003 polaris msx 140 with 105 hrs on blown up center cylinder. wont even turn over. this spring i went through the whole process on a 2002 virage 1200 with rebuilding it. fuel regulator and such but sold it to make some money on it. anyway im going through the process with this one to hopefully keep it.
    question 1. looking at pictures of my pistons. do you think that the fpr falling off would cause this. i know middle cylinder will usually go first but would think other pistons would show a little leaner as well. just trying to figure out of i have injector or emm issue as well.
    question 2. my connecting rod cracked, still attached but cracked. what have people payed for a shop separate crank and install new connecting rod? or am i better off buying a rebuilt crank. thanks
    anything else anybody can suggest to look at or repair while im in on this msx 140
    thank you!
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  2. #2
    Moderator HiPeRcO's Avatar
    Join Date
    Jul 2007
    Upstate NY
    To me that center cylinder looks like mechanical carnage, not a lean burn. The PTO is usually the first to go when the FPR falls off, since it gets fuel "last" in the line. And your black cylinder head is very lean, I assume that is the PTO?

  3. #3
    radio-active's Avatar
    Join Date
    Aug 2018
    What does the head look like -- and the spark plug?

    When my center cylinder melted down, it was because the spark plug disintegrated. Just take one look at that long center electrode and insulator.

    That's why Polaris recommended seasonal changes of all the plugs.
    Last edited by radio-active; 08-27-2020 at 09:51 AM. Reason: spelling

  4. #4
    My spark plug in the middle cylinder is all there nothing broke off or missing. Just some deposits from the carnage.
    The piston in the picture that is all black is pto (rear of engine)which would be bottom in picture. Wouldn't piston being that black indicate rich or atleast not lean burn

  5. #5
    Moderator HiPeRcO's Avatar
    Join Date
    Jul 2007
    Upstate NY
    No, black is lean. Look up "piston wash" to decode cylinder appearances.

  6. #6
    ok thank you. learning more as i go. so i tore the engine completely down. rod is not cracked. but my center cylinder crank bearings are definitely bad. dry and rough spinning all others feel great. i did find that center cylinder oil line had been rubbing on engine and melted shut or leaked. so im guessing hoping that was the failure. still looking for info on crank as replacement? rebuild kits? etc if someone could point me in right direction.
    thank you!

  7. #7
    martincom's Avatar
    Join Date
    May 2010
    Brainerd, MN
    SBT offers re-built cranks. Probably others, but that is what comes to mind.

  8. #8
    yeah i have looked at sbt but have been advised to stay away from them. i have heard mix reviews on sbt products.

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