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  1. #1

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    MSX 150 with low compression but runs 60mph

    Hello,

    I have a stock 04 MSX 150 that has sat since the summer of 2008. This year I replaced the gas, spark plugs, and battery and it started up. It ran very rough at idle. I had to "feather" the gas to keep it running. But at WOT, it ran beautifully. Hit 60 mph. I took it in for what I thought was basic maintenance - oil change, fuel filter change, maybe see if any fuel lines are gummed up. But the shop didn't even get that far.

    They said it only had 80 pounds of compression. They dropped some "ring free" fluid in there overnight and tested it again. This time 90 pounds of compression. The shop isn't sure what else to do and neither am I.

    (1) What should the compression be?

    (2) Is it even possible for the ski to hit 60 mph with only 80 lbs of compression?

    (3) Can you think of any additional issues to troubleshoot?

    At this point, I am stuck with it in my garage and no options. Any advice would be GREATLY appreciated. Thank you in advance.


  2. #2
    jackofalltrades's Avatar
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    Welcome to the hulk. With 80 psi of compression I would suspect nikasil plating failure in the cylinder. The reason you got 90 psi the next day is likely because you added fluid to the cylinder which descreases compression flow past the rings. When the nikasil starts coming off inside the cylinders it collects on the rings and then the cylinder starts to wear rapidly because the cylinder is aluminum.

  3. #3
    slothman's Avatar
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    cylinder compression should be 120-140 in each. Jack is most likely correct, the plating inside the cylinders is probably failing. Time to pull the heads and look at the carnage.

  4. #4

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    Thanks for your help Jack and Sloth. When the Nikasil plating starts to fail, what are your options? Is this something that can be repaired or is the motor trashed? Also, it is possible to start the motor and run it for some time with only 80 pounds of compression? Most people I spoke with said that is impossible. Thanks again. This forum seems to be the only place with clear, sensible answers.

  5. #5
    johnsonmtz's Avatar
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    Quote Originally Posted by DerekMart View Post
    ....When the Nikasil plating starts to fail, what are your options? Is this something that can be repaired or is the motor trashed? Also, it is possible to start the motor and run it for some time with only 80 pounds of compression?
    Rebuilding the engine is your option. This will include having the cylinders replated.

    Continual running of an engine in poor condition will eventually lead to bigger and more expensive problems.

    I have been told the primary reason for the nikasil flaking is due to an excessively rich fuel mapping. There is suppose to be someone that has dug through the ECM code and has developed a reflash that adjusts the mapping tables to make fuel delivery more spot on. The result is better fuel economy and you don't wash away the cylinder plating. I have no firsthand knowledge of how well this works so you would have to research this yourself.

    KJ

  6. #6
    slothman's Avatar
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    Quote Originally Posted by johnsonmtz View Post
    Rebuilding the engine is your option. This will include having the cylinders replated.

    Continual running of an engine in poor condition will eventually lead to bigger and more expensive problems.
    Yep, do not run the engine any more! It's time for a rebuild, or buy a used engine.

  7. #7

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    Quote Originally Posted by DerekMart View Post
    Also, it is possible to start the motor and run it for some time with only 80 pounds of compression? Most people I spoke with said that is impossible.
    Thank for your replies. So just to confirm, hitting top speed with only 80 lbs of compression IS possible? The local mechanics I speak to rule out any major issues because it still is capable at running at WOT.

  8. #8
    Kosh's Avatar
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    Turbos are a magnificent things
    I would check the compression again before you pull the engine apart. Check your gauge or try another one.
    You are not at super high altitude are you?

  9. #9
    slothman's Avatar
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    that's true....60 mph on low compression seems odd...use a different gauge, and test the motor when it is warm...make sure you hold the throttle all the way down when you test it

  10. #10
    Something doesnt sound right...I would HIGHLY recommend that you get another gauge on there as 80 psi is just barely enough to cycle the motor and certainly is not going to run the ski up to 60 mph...that takes some serious HP. A few small engines I have seen in the 70-90 range will barely run and generate maybe 40% of potential power.

    Could you have a top end problem? Sure...but a bad gauge or poor testing procedures may be the cause. I would not pull anything apart until you get to the bottom of this.

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