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  1. #1
    XLTNoob
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    '01 XLT 1200, round two!

    This is the same ski I had the problems with last year, ended up replacing the #2 cylinder, piston, and crankshaft.

    The first time, the engine was filled with flush water, and sat, causing the crankshaft bearings to rust and eventually fail on the #2 cylinder.

    The engine was rebuilt, New crankshaft, buffed the nicks in the crankcase on the #2 cylinder, replaced the #2 cylinder and piston with a used OEM matched pair
    I went out for a ride in clear creek, rode all day. Sometime in the evening, I started out to the creek, engine bogged down and would barely idle, then died. Attempted restart, engine turned over slow like a low battery, but batt was good.

    I decided to swim it back, and on tearing it down at the house, now the #3 cylinder is trash!. Obviously the edge of the head broke off, and the ring apparently spun, but I'm horrible at determining root cause.

    My three scenarios:
    1) #3 cylinder overheated due to lean fuel
    2) #3 cylinder overheated due to lack of water
    3) #3 cylinder spun a ring, and ring caught on the exaust port, ripping the top of the piston.


    Obviously the ring did something dirty causing the majority of the damage, but what do you guys think actually CAUSED the failure?

    Please pay special attention to the underside of the piston, Is this discoloration normal?









    Last edited by Jolly Roger; 05-13-2009 at 05:40 PM.


  2. #2
    YudLuz2's Avatar
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    Looks like your steam broke on your power valve and it dropped
    down on your piston.
    None of your scenarios are correct.

  3. #3
    XLTNoob
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    The powervalve is still operational, it just won't retract all the way up anymore due to the damage. Let me take some pics of that and post them


    EDIT: Looks like the powervalve stem isnt broken.
    Still looking for ideas!


  4. #4
    007GPR08's Avatar
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    YudLuz82, Nice video

  5. #5
    YudLuz2's Avatar
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    I really need another pic of the other side of the power valve.
    The valve is worn a good bit on the stem, thats actually
    enough to drop the valve down enough where it will rub on your piston
    and then catch the ring. The real story is how much play and wear you
    have in that cylinder where the stem goes down into. Other things could have happen, I would need to see the whole motor in person. But your motor would have to be very lean to cause that type of damage to your
    piston. You would also have poor performance and acceleration. Make sure your crank is ok.

  6. #6
    XLTNoob
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    I would not mind mailing you my cylinder/piston/powervalve if it would help diagnose the problem better. It's already removed from the ski.

    I have not noticed it running badly, short of loading at idle. I've got some old pics of the plugs when I was adjusting carbs after the first rebuild, the #3 did not seem to be running lean - but I could be wrong!

    Let me see if I can find those.

  7. #7
    XLTNoob
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    Sorry for the picture quality, cellphone camera
    Before Starting - Date/Time: 2007:09:29 18:51:46
    MAG - CTR - PTO


    IDLE RUN - Date/Time: 2007:09:29 19:02:56
    MAG - CTR - PTO


    WOT RUN - Date/Time: 2007:09:29 18:59:10
    MAG - CTR - PTO


  8. #8
    The other Alex's Avatar
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    Those pictures look exactly like my rear cylinder/piston on my 800 motor that I just finished rebuilding. Powervalves were still intact and operational with one gouge on the top of the valve where it looks like the ring hit it, but both PVs were functioning find and clearing the piston when I was tearing down the motor. I also could not figure out the cause of mine, however when I pulled the carbs off so I can rebuild them, I found a broken reed valve on the intake, whether that was there before the engine blew or not is unknown to me. My ski was running poorly before it blew, like the PVs needed cleaning bad and the carbs rebuilt.

  9. #9
    YudLuz2's Avatar
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    Quote Originally Posted by Jolly Roger View Post
    I would not mind mailing you my cylinder/piston/powervalve if it would help diagnose the problem better. It's already removed from the ski.

    I have not noticed it running badly, short of loading at idle. I've got some old pics of the plugs when I was adjusting carbs after the first rebuild, the #3 did not seem to be running lean - but I could be wrong!

    Let me see if I can find those.
    I would be happy to take at look at the damage parts. I could probably
    help out with some parts if you don't have some already. I have a nice
    oem cylinder and power valve ready to go. You could even trade your core cylinder in for credit, I would just use it for a big bore. P.M. if you
    need my address.

  10. #10
    That PV is in good shape (at least on that side)... That stem is not worn, that section above the valve is a stop and it is up on the shaft a little. It does not start right at the valve section. It keeps the PV from dropping. When it is worn, the stop is usually rounded or broken. Need to see a picture of the others side (top). A second look at that pictures shows a little knick in the curved portion of the PV (bottom of the pic, in the center). It may be from where the ring hit the PV after things came apart...

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