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  1. #1

    MSX 140 missing at mid throttle

    Hi have a MSX 140 going on 55 hrs after my rebuild , very pleased with the ski however I have an engine misfire at around mid throttle sometimes simply working the throttle you can work through the missfire.

    Im thinking maybe a TPS , I hope that's all it is but something tells me maybe the EMM due to the fact it runs great for the first 15 to 20 minutes. This weekend it got worse still runs good but on occasion cuts right back down to idle , beat the throttle again and it runs fine for awhile !

    Any suggestions or where can I buy a TPS and ill start with that ?

    Thanks

    Silverswitch


  2. #2
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    TPS can be bought through a Polaris dealer. Part number 2202740

  3. #3
    Quote Originally Posted by BryanP View Post
    TPS can be bought through a Polaris dealer. Part number 2202740
    got one from my Polaris dealer today , will try it this week
    and let you know !

    Thanks

  4. #4
    Installed the TPS sensor , the ski seems to run great again it still has an occasional hesitation ,but its always had that !
    Ran it a good 20 mins,throttle response seems crisp , motor runs smooth at 2000 to 2500 rpm it seems shaky and rough but i think its the nature of the beast.
    Max rpm seems to be around the 6000 to 6200 range , runs a steady 50 mph to say 55 mph , i only do short top end bursts.
    I bought this ski a few years back , pulled the motor rebuilt it and have about 60 hours on the rebuild now , very pleased with this old ski!
    Thank you yo K447 for his help and BrianP the information and help is priceless!

  5. #5
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Silverswitch View Post
    Installed the TPS sensor , the ski seems to run great again it still has an occasional hesitation ,but its always had that !
    Ran it a good 20 mins,throttle response seems crisp , motor runs smooth at 2000 to 2500 rpm it seems shaky and rough but i think its the nature of the beast.

    Max rpm seems to be around the 6000 to 6200 range , runs a steady 50 mph to say 55 mph , i only do short top end bursts.

    I bought this ski a few years back , pulled the motor rebuilt it and have about 60 hours on the rebuild now , very pleased with this old ski!

    Thank you to K447 for his help and BrianP the information and help is priceless!
    Max RPM on that engine should be more like 6700RPM, maybe even a bit higher.

    When the engine was rebuilt, were the cylinders sleeved or re-Nikasiled?

    What pistons were installed?

    Is the jet pump stock, with stock impeller?

  6. #6
    Hi K447 . the cylinders went to CV Tech for re -Nic the pistons are WSM
    I have no clue on the impellar or jet pump?

    thanks

  7. #7
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Silverswitch View Post
    ...
    I have no clue on the impeller or jet pump?
    ...
    Well, next time you have the jet pump out, check the part number on the impeller hub. If the wrong impeller is in there it can drag engine RPM down, and reduce proper thrust and engine power.

    If the impeller is correct, then your engine is down on power for some reason.

    When you did the engine rebuild, did you also rebuild the jet pump bearings and seals, and rebuild the through-hull bearing carier? If not, now or soon would be a good time

  8. #8
    I replaced the thru hull bearing and a shaft seal only. I will check the impellar number this fall , what should number should it be ?
    Since my engine rebuild the rpm's have stayed consistent at say 6000 rpm , maybe you are correct the impellar could need service or wrong pitch.
    The motor seems to run fine idles rock solid at 1200 rpm and runs crisp and clean .Not sure what would cause the engine to be down on power?
    Not sure if any updates have been performed on this unit ?

  9. #9
    Getting this MSX figured out, got my 6600 rpms throttle body was not opening fully. Still have a miss that causes the rpms to drop back to 6000 rpm , o2 sensor looks really bad, will cut out the TPS plug and marette the TPS wires.
    Also thinking of new plug wires and coils over the winter

  10. #10
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by Silverswitch View Post
    Getting this MSX figured out, got my 6600 rpms throttle body was not opening fully. Still have a miss that causes the rpms to drop back to 6000 rpm ,

    o2 sensor looks really bad,

    will cut out the TPS plug and marette the TPS wires.

    Also thinking of new plug wires and coils over the winter
    There is no oxygen sensor on the MSX 140 engine.

    I am not a fan of using marette connections in a watercraft.

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