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  1. #1

    yet another 1994 Polaris SL 750 jet ski project

    Hi guys,
    I recently bought Polaris SL 750. I've been told by seller the engine runs rough. After quick googling I've found this forum and I got many answers to my questions here . I measured compression and found two cylinders get about 110 psi on cold engine and the third and gets 0 psi. Following recommendations I found here I opened dome and took few pictures. It looks to to me like piston is lean. Also internal dome surface has a scratches. Need your advise to diagnose the problem and create the shopping list to start rebuild. I read here the top end can be rebuilt without taking the engine out of the hull. Is that correct?
    So far based on ph2ocraft article I would like to replace fuel pump to triple outlet fuel pump, looks like I need top end replacement kit too. But here is a question what size do I have to order?

    Thanks in advance,
    Artiom
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    Last edited by Artiom; 07-18-2007 at 11:13 AM.


  2. #2
    Bing-A-Ding-Ding-Ding, Brrrrrap! Brrrrrrrrrap!!! Polaris_Nut#1's Avatar
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    yes the top end can be replaced in the craft. you have to have your cylinders measured for wear before you will know what size to order.

  3. #3
    Thanks.
    How can I measure the cylinder? What equipment do I need?


    Artiom

  4. #4
    Looks like a hole in the head. can you take clear pictures of the head again?

  5. #5
    Good catch ! It is not a hole - it's a piece of the ring (see attached pictures). This pretty much explain why pistol is so flexible in the cylinder. I'm going to remove cylinder to explore the surface.

    Thanks
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  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    If the rings broke, metal frags may be in the crank bearings. That would be very bad. How does it sound as you turn it over by hand? Any grit would shorten your crank's life drastically.

  7. #7
    It doesn't make any suspicious sound when it turns. How can I verify that there are no fragments left in the engine?

  8. #8
    nothing short of a tear down and inspection of the crank , case and bearings. you will find something

  9. #9
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    I'm afraid he's right. ^^^^ You can chance it, but the proper way would be to tear it all down. Do you feel lucky?

  10. #10
    Like usual - yes I do feel lucky. I just opened this cylinder. The upper ring doesn't exists at all. Big piece of the lower one still in the socket. The piston on top and dome both are significantly scratched but cylinder looks inside pretty good. I hope the majority of the broken ring has been eaten in top end.

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