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  1. #1

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    03 MSX 140 Motor Failure - Need Help

    Look these pix over and give me your best Diagnosis on the root cause. All three pistons are toasted on the intake side.

    Motor entirely (top to bottom) re-built at 103 hours. At 105 hours, Mag. let's go. New mag. re-build and new fuel pump.

    At this time, center and PTO look OK, but at 105 psi. Decided to just re-build Mag.

    Ran all last year. (30 hours and i am sure some/most of it with the top end in some state of blown-up)

    There is freash oil at the base of the throtle bodies, it appears my oil pump works, my TPS in new at 103 hours, and when it did run, my idle would go 1150, 900, 800, 1150, 750, 1150, 750, 1150, 700, then the ski would die.

    Going to re-new the top end and need any advise on what else to open up and look at. HELP!!!!!!!!!!


    Tom
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  2. #2

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    More Pix

    Some More.
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  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Don't downsize photos when attaching them. Shrinking them to 640x480 make it harder to see the details.

    Provide more info regarding the rebuild at 103 hours. It sounds like something was not quite right.

    What was the compression right after the 103 hour rebuild?

    What exactly happened to the MAG piston at 105 hours?
    105 PSI on the other two cylinders sounds really low.

    Was the idle unstable since the 103 hour rebuild?

    Have you checked fuel pressure?

  4. #4
    Connecticut CrazyA's Avatar
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    With all three slugs being in that condition on the intake side, I would doublecheck your lubrication system.

    Did the ski ever take on water or have any leaks anywhere that you're aware of?

    When the ski was rebuilt at 103hrs, how was the condition of the cylinder surfaces? Glazed over? Scored?

  5. #5

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    I will take some better pix and post them. I got the ski and the motor was apart. The the Mag. had nuked and took out the head, rod, cylinder, crank, and snapped an ear off the case.

    New crank, welded case and matched it, new cylinder, head. All new pistons. The mag. was so far gone, not sure you could determine the cause. Other pistons looked like they could have gone back on. Had all three cylinders honed and cleaned.

    There is raw oil below my air cleaner and a rather large amount of milky oil stuff sloshing around.

    It has only been unside down once, so other than that, no water ingestion. It looks like a lube problem, bad reed cages, or maybe an air leak.

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Koodat View Post
    ...a rather large amount of milky oil stuff sloshing around...
    That would be water mixed with oil.

    Perhaps there was gasket leakage, allowing cooling water to get into the engine

    On an MSX 140 engine, that would mean cylinder head or exhaust manifold gaskets.

    Other than the overturn incident, was it normal to find water inside the hull after riding?

    Was the metal cover over the drive shaft coupler in place?

  7. #7

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    Yes the cover in on the coupler. I was thinking about when the ski is not running and the possibility of water ingestion when towing or such. If your firends turn the ski off too soon and it is coasting into shore, can water back-up into the motor like I have read?

    How do I ensure that water does not back up into the moto? I had all new gaskets put in last go around, so not sure that is it. All new gaskets going in again as well. I think it is fuel related or a leak. Then will go move onto the fule pump and regulator. Lastly is the EMM. Hope I don't have to go there.

    Anybody else?

  8. #8
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Koodat View Post
    ...I was thinking about when the ski is not running and the possibility of water ingestion when towing or such.

    If your friends turn the ski off too soon and it is coasting into shore, can water back-up into the motor...?
    I don't think it would, just from coasting to a stop

    How do I ensure that water does not back up into the motor?

    I had all new gaskets put in last go around, so not sure that is it. All new gaskets going in again as well. I think it is fuel related or a leak.

    Then will go move onto the fuel pump and regulator. Lastly is the EMM. Hope I don't have to go there...
    Make sure the sealing surfaces are flat and true. Gaskets won't seal properly if the mating surfaces are warped, rough, or uneven.

    You can pressure test the rebuilt engine. Seal up the intake and exhaust, and small openings like the front crank oil feed nipple. Apply a few PSI pressure or vacuum.

    Close off the pressure/vacuum pump, and watch the gauge for pressure change. A well sealed engine should leak down very slowly. Search for leak down for more info.

    You can also pressure test the water jackets, just to be sure.

  9. #9
    SPEED KILLS, BUT YOU GET THERE QUICKER Keddano's Avatar
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    What's the odds that it sucked some weeds or something? I'm thinking you overheated it to catch all 3 cyls.

  10. #10

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    Strange that all 3 on the intake side are you sure that its oil in the lower and not fuel?
    Its very ODD that the pistons are new they look like there worn out on the ex side.
    Man the pistons are warn out looking at the exhaust side Big Time other them the damage on the front or intake side.
    I rebuilt my 140 after 300 hours they they did not look that Bad.

    I would double check
    1. Oil pump output
    2. Did who ever put the engine together pressure test with the intake manifold on? (Air Leak)
    3. Did someone leave out the gaskets under the (carbs Air Leak if So)
    4. On exhaust manifold the heat sensor (could be bad causing a lean condition)
    5. How about the 3 brass plugs at the lower intake side of the cases did someone take them out and re-install them.
    6. What case sealer did you use when you put the cases together? Three bond 1211 is a MUST if you used Yamabond or Three bond 1104 its VERY possible that you have a air leak these Big Polaris motors vibrate (Air Leak) 1210 should also be used on the reed valves and intake manifold the standard seal or built in O-ring just goes bad after time (Air Leak)
    7. When you pulled the engine Did you have the jet pump OFF?? is the small white plastic restrictor in the waterline? check out number 7 in the Diagram.


    When you I will keep thinking and if I can come up with something else I will post it.
    As you know our Polaris MSX 140's are great boats once you get it taken care of you will be happy keep after it.
    I have 2 stocks 140's, 1 Matrix and 1 Matrix Extreme and I love them.
    Good Luck

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