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  1. #1
    john07ex's Avatar
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    HELP.. 07 FX ho broke

    My buddy has a stock FX with 20 hours on it and it just broke while playing in a lake. It started to miss and wouldnt go over 40mph. Took intake cover off and it had oil all over air filter.. read about oil overfilled. Changed the oil and cleaned the intake and replaced the plugs..
    same problem..The dealer did a compression test and cylinder #2 was zero. They pulled the heads and a piston has slapped the head..

    WHY??

    Anyone have any ideas on how this could of happened with such LOW hours on a stock ski. Can he get yamaha to cover any of it being out of warranty?


  2. #2
    I've seen one theory that overfilling the oil on this model puts more stress on con rods etc. as the scavenging system is not able to remove excess oil from the crankcase fast enough........sort of an internal hydrolock........don't know if this is valid, but have heard it from Yamaha mechanic.

    Other reason very common on low hour ski, is piston rings and valves corrode due to moisture from the exhaust. That is one reason Yamaha and many smart guys recommend fogging the engine if the ski will not be ridden for a month or more..........definitely happened on a 07 with only 20 hours.

    Chance of Yamaha covering it between slim and none.

  3. #3
    john07ex's Avatar
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    the 10hr service was done by yamaha dealer and he ran it for 13hrs on that oil level with no problems..

  4. #4
    Kelly_A's Avatar
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    You need more info to narrow down cause. "Piston has slapped the head" doesn't tell you much. I'm guessing the #2 connecting rod broke?

    I suppose there's a slim chance the #2 connecting rod assembly was improperly torqued at the factory and loosened to the point the piston was able to contact the valves or head. If this were the case, you might get somewhere with Yamaha - not likely, but not impossible.

    When you pulled the plugs trying to diagnose the problem, didn't you notice the #2 plug electrode was flattened?

  5. #5
    john07ex's Avatar
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    The plugs were fine. And that's my theory also.. it was a factory DUD.

  6. #6
    john07ex's Avatar
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    It seems one piston is actually loose.. you can wiggle it side to side by hand. Dont these engines have some special coated cylinder sleeve that could be bad from the factory?

  7. #7
    Kelly_A's Avatar
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    Quote Originally Posted by john07ex View Post
    It seems one piston is actually loose.. you can wiggle it side to side by hand. Dont these engines have some special coated cylinder sleeve that could be bad from the factory?
    I'm not sure about the coating. Side to side movement in the cylinder would almost have to be from broken/seized rings.

    You'll need the dealer on your side in this if you expect Yamaha to do anything at all. You need to check and see if the if the connecting rod assemble to to crankshaft connection failed, the rings seized/broke or the connecting rod broke.

  8. #8
    john07ex's Avatar
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    Quote Originally Posted by Kelly_A View Post
    I'm not sure about the coating. Side to side movement in the cylinder would almost have to be from broken/seized rings.

    You'll need the dealer on your side in this if you expect Yamaha to do anything at all. You need to check and see if the if the connecting rod assemble to to crankshaft connection failed, the rings seized/broke or the connecting rod broke.
    Faith has been restored ..yamaha is going to rebuild it for free..

    my next ski will be a yamaha for sure..

  9. #9
    YoYamma's Avatar
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    Glad to hear they are standing behind it...
    I noticed you said it was out of warranty; was this ski purchased by your friend in 2007?

  10. #10
    Kelly_A's Avatar
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    wow, great outcome!

    What exactly had happened to cause the piston to hit the head?

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