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  1. #1

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    Ski blew up again need some help

    Well number 1 cylinder blew again . Orignally ski ran great all summer decided to put on a decked head at the end of the summer I went out soft seized number 1 at wide open . Before I even came to a stop I could start it right back up .I found a torn pulse line so I pulled the head honed the cylinders reringed all 3 replaced all the lines . I went out to break it in ran great on/off the throttle for about an hr went fine plugs looked good . Went home retorqued everything ,couple weeks later I went out on off the throttle for about half hr . Then I held it wide open for longer period of time I would say half mile to a mile then it died again same thing would start right back up . Same type of seizure both times piston is chipped up along the exhasut side edge . Iam not sure what the cause is ,if something has gone wrong in the carb or if i have some kind of water ingestion the motor is an sbt motor . Carbs have been jetted with t handles . When i got the ski supposedly front carb was rebuilt and the back two carbs where replaced .
    Here are some pics



    piston wash on the other 2


  2. #2
    Moderator RX951's Avatar
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    Dang, sorry to hear.

    question.....uh, looking at those pics, are those base gaskets OEM Yamaha gaskets? I have not seen those color before. I normally see them as a grayish black.

    also the carb base gasket.....it is in good shape? did you replace it as well from the carb rebuild?

  3. #3
    YudLuz2's Avatar
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    You have deto all over the exhaust side of the piston. Cause by either lean condition or poor octane. Are you using 93 octane?
    Billy, it looks like he is using copper coating on the base gaskets.

  4. #4
    WATER WOODY's Avatar
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    I would check the #1 carb that was rebuilt. Verify the jetting etc.....
    Motor must be pressure tested after its put together.

  5. #5
    Moderator RX951's Avatar
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    Quote Originally Posted by YudLuz2 View Post
    Billy, it looks like he is using copper coating on the base gaskets.
    aH...thanks Ben

  6. #6

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    Yes it is copper coat on the gaskets . The carb gaskets where all new when I put the jets in the carbs before the summer and it ran great all summer , I use 93 octane , jets are 110 lows 125 mains.

  7. #7

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    I have not had time to pull the carbs yet but the main reason i think its a problem with the 1 carb is because after the first 30 to 45 min ride on the rebuild i did a compresion check it was ok 150 across all 3 . I just never held it flat out for any longer than a few seconds on the first ride . But when i did it pops that front cylinder . Other mods to fuel system no petcock , no flapper , running off of the reserve pickup primer is of the other pickup in the tank . I figure if it was a fuel feed problem I would have problems with the other 2 cylinders.

  8. #8

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    Quote Originally Posted by WATER WOODY View Post
    I would check the #1 carb that was rebuilt. Verify the jetting etc.....
    Motor must be pressure tested after its put together.

    When i do go back together again i have a differential pressure tester to put pressure in the cylinder . What can i use to plug the intake and exhaust ?

  9. #9
    WATER WOODY's Avatar
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    Quote Originally Posted by harleyboy61 View Post
    When i do go back together again i have a differential pressure tester to put pressure in the cylinder . What can i use to plug the intake and exhaust ?

    No, you need to pressure test the entire engine. Contact me or Lowell Horning for the kit.

  10. #10
    YudLuz2's Avatar
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    Whats your low and high speed screws set on carb 1 ?
    I see you have ported cylinders, I would go at least 1 turn out more on your high speed screws and see if your rpms go up or down.

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