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  1. #1

    Wink 99 GSX LTD What caused this damage

    Take a look a the damage to the pistons in the attached photo's.

    Click image for larger version. 

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    What might have caused this damage, there were bits of metal in one of the spark plugs but i cannot find where it came from. I intially thought that maybe a rod bearing had let go but all good there. Rave valves are perfect and all rings are fully intact. head also has similar damage. From experience this damage is usually caused by metal impacting the pistons but where the hell has it come from.

    Notice that the damage is only on the outer edge of the pistons. Also this ski was sank by the owner sometime back (he forgot to insert the plugs)


  2. #2
    Click image for larger version. 

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ID:	205745PIc of head damage

  3. #3
    RumRunnerRon's Avatar
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    Quote Originally Posted by steelroe View Post
    Take a look a the damage to the pistons in the attached photo's.

    Click image for larger version. 

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ID:	205726Click image for larger version. 

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    What might have caused this damage, there were bits of metal in one of the spark plugs but i cannot find where it came from. I intially thought that maybe a rod bearing had let go but all good there. Rave valves are perfect and all rings are fully intact. head also has similar damage. From experience this damage is usually caused by metal impacting the pistons but where the hell has it come from.

    Notice that the damage is only on the outer edge of the pistons. Also this ski was sank by the owner sometime back (he forgot to insert the plugs)

    Im just stating an opinion here so take it easy guys if I'm wrong but, could water ingestion have something to do with it. Boat was sank once the PO may have done it more than once. That might explain why the pistons are so clean on top and you have burnt pistons. At least it looks like meltage to me. The damage just doesn't look like impact marks like something cut loose. Water ingestion would lean you out. Just a thought.

  4. #4
    This is a ski I have in for repair. I am just a bit baffled as to what might have caused the damge to the pistons. They look like they hve been hit with small ball bearings.

  5. #5
    RumRunnerRon's Avatar
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    Quote Originally Posted by steelroe View Post
    This is a ski I have in for repair. I am just a bit baffled as to what might have caused the damge to the pistons. They look like they hve been hit with small ball bearings.


    I would think there would me more damage to the head if bearings cut loose and found there way into the combustion chamber. If you didn't clean off the head and pistons they sure look clean and that doesn't look right either. Unless there are just no hours on that engine . Ask around and if need be bump your thread to keep it at the top. There certainly are others with more experience than I. Good luck with it.

  6. #6
    I did clean the pistons to show the damage more clearly.

  7. #7
    mibunkerking's Avatar
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    that looks like DETO. too tight squish is my guess.

  8. #8
    flyin' the friendly skies airbornexp's Avatar
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    wrist pin bearing may have caused that...but it looks like the beginning of a lean seizure to me

  9. #9
    ktyamaha36's Avatar
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    X2 on the wrist pin bearings. Turn the crank back and fourth and you should be able to hear the slop in the piston. Not only will it need a whole top end but you have to pull the engine and split the case to find all the little needle bearings that fell to the bottom. I find this to be very common on 951's. I have rebuilt quite a few that had the exact damage. Although it is odd that its only on the outside of the piston. Click image for larger version. 

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    Just had this one happen last week.

  10. #10
    SURFnTURF's Avatar
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    One of two things either wrist pins have done the damage(don't think as no longitudinal marks on the piston/head) or detonation from lean or tight squish clearance.If it was mine I would pull the bottom end and have a look around just to have some peace of mind.

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