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  1. #1

    What caused the damage to my piston? Pics Inside

    Hi Everyone,

    My name is Geoff, I just bought a '95 Seadoo Speedster with Twin 657Xs. Its my first boat, however, Iam an auto mechanic so it shouldnt be too difficult to get her running again.

    I did a compression test and Engine #1 has 140psi on both cyls, Engine #2 has 30psi on the MAG side and 135psi on the PTO side. Iam at 5500ft of Air so the numbers will be alittle low.

    Anyhow, I took the head off and have posted a few pictures to see if you guys can help me figure out the cause of death for my piston. It obviously has a broken crown/ring land...but im not sure why...havent worked on a 2 stroke in years.

    Im planning on purchasing a new top-end kit this week.

    Thanks for any and all help!
    -Geoff



  2. #2
    kecheme's Avatar
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    My best guess is a lean condition. Like a clog filter in the carbs. Its just a SWAG. Go thru carbs and check all jets, needles,filters,etc.

  3. #3

    Join Date
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    Ya my guess would be the same it looks like a lean condition. Definitely take the carbs apart and go thru them.

  4. #4
    UPDATE:

    I decided to inspect the bottom-end so I split the cases and found both bearings on the MAG side of the crank were shot...My best guess is that the shot bearings allowed the crank to move around which killed the crank oil seal and let in air which leaned out the cylinder and melted the piston.

    Since this engine was the original engine for the boat and has 15+ years of abuse on it, Im guessing it had at least 400-500hours on it, so it was time for a replacement anyhow. Hopefully the other engine doesnt let go anytime soon.

    On another note, both Jets look perfect. Wear Rings have no visible or physical ridges, divets, etc. Impellers have sharp edges and by no physical damage. By the looks of everything is looks as if it was a well maintained boat.

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