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  1. #1

    Flipped my 780 SLX

    I flipped My 780 SLX when I lost power in a sharp turn.Anyway I have a hole on the side of the middle piston in between the rings and wanted to know if the wrong size piston could cause this?


  2. #2
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Can ya post a pic of it and the cylinder?

  3. #3
    Sure will thanks for the quick reply pics on the way

  4. #4

    780 hole in piston side

    Here the pics sorry for the quality.Also the piston skirts fit real loose when inserted backwards into the cylinder lots of slack side to side.Johnny Rod
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  5. #5
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Looks like it was running lean, and ring snagged the boost port? How many hrs on that? What brand of piston is that? Oem and the WSM's I have dont have that cooling port on the piston. Did you by chance pull the other domes? Can we get a high res pic of the cylinder. Particularly of the ports? And the other piston tops?

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Holy crap!!!!!!

    Piston to cyl wall limit is .008" unless it's a Wiseco.


    Star, those aren't cooling ports. They are more of a weight savings.

    Polaris pistons have them, and my old Wisecos have them. The new Wisecos Do Not. That's why I needed the one from Al's old stock when mine seized.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Does the ski have mods done to it? High compression heads etc...

    Did it overheat?

    Is it premix?

    How do the others look?

  8. #8
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    I could have sworn I read that holes that went through the side of the pistons were cooling ports. Somehow helped cool the dome of the piston. Not sure I understand how.
    Anyhow, heres a pic of an oem piston, and it has an indentation on the side in the cast, but doesn't go all the way through the side. His looked as if they were all the way through.
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  9. #9
    Lake Mead Bum & BTLS Mark starflight's Avatar
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    Quote Originally Posted by xlint89 View Post
    Holy crap!!!!!!

    Star, those aren't cooling ports. They are more of a weight savings.
    Here is what I've read on the piston cooling ports. Look at Graham Bell Porting .pdf pages 39-40 located here... http://www.greenhulk.net/forums/show...t=15460&page=3
    They are typically lined up w/ boost ports for extra piston cooling.

    Took me a while to remember where I read it.

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