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  1. #1

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    03 MSX 140, need a little help

    I have an 03 140 with 46 hours on it. Last year I just got done rebuilding the front end, the flywheel gernaded and took out the stator. I put about 5 hours on it after that, everything was great. One night I was riding around about 5500 and all of a sudden I started to lose power, no check engine light, no nothing. I was able to only run it at about 3800 rpm, it sounded like the rev limiter was cutting it out. I've checked fuel pressure, it was good at 25psi. I replaced the TPS, and took it out today and the problem persists, does anyone have any suggestions? The ski idles fine so I don't think I've dropped a cylinder, is there any sort of cut out protection feature that limits the RPM to the 3800 rpm area?


  2. #2

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    I'm starting to think it's a bad water temp sensor? No warning lights on whatsoever.

  3. #3
    Click avatar for tech links/info, donation request K447's Avatar
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    Check compression. If there is a mechanical problem you need to know about it.

    You can read the EMM for codes. Not all problems will trigger the display warnings. The LED tool instructions can be found via my signature links.

    That said, some EMM internal failures do not trigger trouble codes.

    Will it rev to near redline when out of the water? Do all three cylinders get equally hot when you run it?

    Correct spark plugs installed?

  4. #4

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    Thanks, I'll check that out tomorrow. It just seemed strange when it happened, I thought I lost my fp regulator, it just lost 2000 rpm when I was cruising down the river, but it motored back to the dock ok.

  5. #5

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    Thanks K447, I was ignoring basics. I did a compression test and had zero compression on cyl#3. I pulled the head off and found the piston had burned. My next question, what was the culprit of the burning??? Fuel mixture? Also, I'm nowhere near a Polaris dealer, do you have any recommendations on the best place to get parts? I know I'll need a new piston, rings, lower jug gasket, head o-ring and gaskets for the cooling jacket. Anything else, should I replace the wrist pin or does the new piston come with it?

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  6. #6
    urugol's Avatar
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    Quote Originally Posted by echampion76 View Post
    Thanks K447, I was ignoring basics. I did a compression test and had zero compression on cyl#3. I pulled the head off and found the piston had burned. My next question, what was the culprit of the burning??? Fuel mixture? Also, I'm nowhere near a Polaris dealer, do you have any recommendations on the best place to get parts? I know I'll need a new piston, rings, lower jug gasket, head o-ring and gaskets for the cooling jacket. Anything else, should I replace the wrist pin or does the new piston come with it?
    You will need a piston kit, meaning new piston, rings, clips and bearing. Change the wrist pin as well. You will at minimum need a cylinder hone, at most a renic. You can get parts from partspitstop.com oem polaris or aftermarket, having just gone through this the aftermarket options are not very good for these pistons but they are interchangeable with certain polaris 800cc sleds. Oem is still fairly priced though. Looking at the damage it's best to make certain there is no debris that has fallen into tat crank case. That's the last thing you want when doing the rebuild. Did you get comp numbers on the oter 2 cyls? If they are borderline it would be best to at least re-ring the entire top end now that you have the chance too.

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    What does the piston wash pattern look like on the other two pistons? If those are showing lean that might tell us something.

    Since you already checked fuel pressure the question goes something like this;
    Did it run lean and the lean caused the piston failure?
    Did the piston fail for some other reason? Broken ring, just old age, brittle...

    If it was lean caused, and fuel pressure is good, then what? Injector weakened? EMM not driving that injector properly? Is the EMM 45 volt output to power the injectors weak?

    I suppose it is possible for the fuel pump to show good fuel pressure when engine is not running or running at idle, yet not be able to keep up when the engine is demanding more fuel at high RPM.

    Back to basics - what was compression when you repaired the flywheel and stator?

    Did you replace both flywheel and stator?

    Are the fuel lines to the injectors, especially the rear injector, all in good shape? No kinks or abrasion where they rub the injector brackets?

    Has the EMM ever been serviced/checked/repaired?

  8. #8

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    Also look at crank seal and make sure it's good. If the other 2 cyls. have good wash the seal could be bad on the pto end.

  9. #9
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by ed1050 View Post
    Also look at crank seal and make sure it's good.

    If the other 2 cyls. have good wash the seal could be bad on the pto end.
    Always good to inspect the seals, of course. And you do want the seals to be in good condition.

    Keep in mind that unlike a carburetor engine the Ficht engines are not bothered so much by an air leak. Fuel delivery is calculated and delivered through the injector based on RPM and throttle position, even if some air might be getting in past a crank seal and not going through the throttle body.

    Note the large holes in the Ficht throttle plates. Lots of air flow even with throttle closed. Yet a Ficht engine idles well because the EMM is controlling fuel injection carefully.

  10. #10

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    Quote Originally Posted by K447 View Post
    What does the piston wash pattern look like on the other two pistons? If those are showing lean that might tell us something.

    Since you already checked fuel pressure the question goes something like this;
    Did it run lean and the lean caused the piston failure? That's what I'm wondering.
    Did the piston fail for some other reason? Broken ring, just old age, brittle... the ring wasn't broken so I don't think it has anything to do with ring failure

    If it was lean caused, and fuel pressure is good, then what? Injector weakened? EMM not driving that injector properly? Is the EMM 45 volt output to power the injectors weak? I'll have to check that once I get it running again.

    I suppose it is possible for the fuel pump to show good fuel pressure when engine is not running or running at idle, yet not be able to keep up when the engine is demanding more fuel at high RPM. Hard to say, it was really hard for me to test the fuel pressure out of the water, my water source was a 60 mile round trip. All I can tell you is that I spliced in the inline Kawi regulator and I'm now running about 35 lbs of pressure. I put this on since I burned the hole in the piston.

    Back to basics - what was compression when you repaired the flywheel and stator? Don't remember, that was 12 months ago. I checked the compression yesterday, will all the plugs out I was getting 120 psi on cyls #1 and #2

    Did you replace both flywheel and stator? AZ west powersports replaced my flywheel, stator and starter 12 months ago.

    Are the fuel lines to the injectors, especially the rear injector, all in good shape? No kinks or abrasion where they rub the injector brackets? Yes, the fuel lines look like new.

    Has the EMM ever been serviced/checked/repaired?
    When I was having the problem with the failed stator last summer I sent out my EMM to DFI and they checked it, they found no problems and sent it back.


    Thanks again for all your help, I'm thinking about replacing all 3 but with 46 hours on it and great compression I don't know if I should fix something that isn't broken.

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