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  1. #1

    Unhappy chipped piston with hole burnt thru it on msx 140!help

    hi,I have 2003 polaris msx140 with 113 hours that I bought with the engine blown.it would start and run and idle but only for about 30 seconds unless you revved it.I have worked on these things for a while but this one has me puzzled! my question is what caused this damage? the top of the piston is chunked out on the exhaust side with broken rings and hole burnt thru the piston in between where the two rings are! this is the center cylinder btw. the other two cylinders looked good but compression was kinda low 130 and 110/120 on the other.ive ordered the top end kit from sbt for it and just want to know what caused this so it doesnt happen again. K447 i see you are experienced with polarisand have many posts...any ideas buddy?please help


  2. #2
    2&4strokepolaristech's Avatar
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    Please check your fuel pressure. there is a fitting on the return line going back to the fuel tank on the lines off the injectors. You should have 20-30 psi. Most cases they operate at 22-23psi. If you have no pressure your regulator fell off and is probably laying in the bottom of the fuel tank. Some people repair them and others pump a new pump on. This is a goo place to start. Also you should be running premium fuel in the unit...no less than 89. Old gas from sitting through the winter losses the octane very fast. The government will tell you fuel is only good for 30 days out of the pump!!!!

    The MSX should have a compression reading of 125 psi when in good condition. The heads are very big in CC's

    Hope this helps

    Jay

  3. #3
    Thanks jay I will check that for sure.but if the recitifier has fell off will it run?I guess I'm wondering what exactly it does or its purpose? Would this cause it to lean out and do this?plus its only the center piston/that was affected.could it be the injector,bad gas,or something else?could this have been a ring snag then it being ran a while after the damage caused the burnt hole in the side? Any input is greatly appreciated

  4. #4
    Sorry I meant regulater where I wrote recitifier in the above post

  5. #5
    Ok I went thru the hellacious task of removeing the fuel pump just to see if the regulator had fallen off.there was nothing in the bottom of tank that I could see thru the hole where fuel pump goes.I'm not even sure what the regulator looks like,could someone tell me so I can make sure I know what I'm looking at?guess ill have to wait till I get the engine installed to check the fuel pressure.i will post pics of the damaged piston and cylinder tomorrow

  6. #6
    Click avatar for tech links/info, donation request K447's Avatar
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    Quote Originally Posted by 2000 gtx rfi View Post
    Ok I went thru the hellacious task of removing the fuel pump just to see if the regulator had fallen off.

    there was nothing in the bottom of tank that I could see thru the hole where fuel pump goes.I'm not even sure what the regulator looks like, could someone tell me so I can make sure I know what I'm looking at?

    guess ill have to wait till I get the engine installed to check the fuel pressure.

    i will post pics of the damaged piston and cylinder tomorrow
    Polaris Ficht Fuel Injected Engines

    How to repair a Ficht fuel pump - pressure regulator has fallen inside

  7. #7

    pics of damaged piston


  8. #8

  9. #9

  10. #10

    pic of the cylinder


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