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  1. #1

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    Help i lost compression

    Well i went out today and the ski stopped i let cool it started right back up . I got home lost compression in the front cylinder the other 2 are 160 . I think there is something wrong with the front carb . My question is should i just redo the one cylinder or should i pull the other two also ? Now it does have sleeved cylinders from sbt when i had the head off i did notice i can move the pistons back and forth in all cylinders is this normal ? If i bore all 3 how big can i go with it and keep it reliable ?


  2. #2
    Banned User
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    Other two are probably ok but you need to check for scoring. The crank will also need to be inspected.

  3. #3
    L Carlson's Avatar
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    post pics. How many hrs? on the top end? Pre mixing the fuel?

  4. #4

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    Quote Originally Posted by L Carlson View Post
    post pics. How many hrs? on the top end? Pre mixing the fuel?

    I would say about 40hrs on the motor . It is premix 40:1 . i dont have it apart yet once i do i will post some pics . Just not sure if i should redo all 3 or just the 1 cylinder . The thing i dont like about the 2 good cylinders i can take my hand and move the piston back and forth in the bore . I have built many 4 stroke motors and some 2 stroke , I know there is supposed to be some movement ,but never noticed that much slop before . Is this common for jetski because of the rates of expansion ? I dont want to get it back together then have a different cylinder let go .

  5. #5
    1- Pics will help us diagnose what caused the damage (lean condition, water ingestion, etc) before you take apart the engine its a good idea to do a pressure test to see if an air or water leak caused the damage.
    2- I would remove all three cylinders, to check proper clearance of the other two good cylinders.
    3- It is normal to have some movement of piston inside the cylinder, in order to know whats too much or too little you must check all clearance specs.
    4- If the other two cylinders are good. I would only repair the damaged one. The problem is, you have sleeved cylinders so you just can't replate it. Either re-sleeve or bore up or maybe get another sleeved cylinder of the same size. What size are yours?

    If going up on bore size, I think its always better to have all three cylinders at the same size for balance. But maybe if the difference its small it could be ok. Don't know how much of difference in size between cylinders its acceptable, someone else here could know?

    Also post your jetting and mods to have an idea...

  6. #6

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    Quote Originally Posted by chris1200 View Post
    1- Pics will help us diagnose what caused the damage (lean condition, water ingestion, etc) before you take apart the engine its a good idea to do a pressure test to see if an air or water leak caused the damage.
    2- I would remove all three cylinders, to check proper clearance of the other two good cylinders.
    3- It is normal to have some movement of piston inside the cylinder, in order to know whats too much or too little you must check all clearance specs.
    4- If the other two cylinders are good. I would only repair the damaged one. The problem is, you have sleeved cylinders so you just can't replate it. Either re-sleeve or bore up or maybe get another sleeved cylinder of the same size. What size are yours?

    If going up on bore size, I think its always better to have all three cylinders at the same size for balance. But maybe if the difference its small it could be ok. Don't know how much of difference in size between cylinders its acceptable, someone else here could know?

    Also post your jetting and mods to have an idea...
    iam going to pull the head today i do believe it is stock bore i will get some pics as soon as i get the head off .

    If i go up to a 1300 bore on all 3 cylinders can i still use the decked head i have or will it have to be recut again .

    jetting i have f/a no outerwears , choke plates removed jet kit by island racing i installed jets ski ran great all summer . i think the jets are 110 lows 125 highs and 1.5 needle and seats silver springs

  7. #7
    If going 1300 size, both head and head gasket will need to be cut open to 84mm, a 1300 OEM gasket will not fit properly.

  8. #8

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    pics



    here are some pics of the front cylinder

  9. #9
    sleeplessnMS's Avatar
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    looks like water intrusion....

  10. #10

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    Quote Originally Posted by sleeplessnMS View Post
    looks like water intrusion....
    do you think being lean could have caused that ?

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