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  1. #1

    Join Date
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    Polaris Piston oversize .75

    I have a 1996 780SLX engine that I am putting together and the pistons on it are OEM Polaris with stampings 78A and .75 (oversize). I have one bad piston and would like to replace with same. Looked up online using this site http://parts.polarisind.com/Browse/Browse.aspnd and the only oversize Polaris has is .25 and .50 but not .75 . Called dealer and they told me that manufacturers usually only make .25 and .50 oversize and they could not find .75 . If 78A means they are Polaris OEM then do I have a discontinued piston or a snowmobile piston? Or are these not OEM? Are there any other sources to find same piston? I tried Neilsen Enterprises and no luck. Also tried another dealer in Twin Lakes, WI and they cannot lookup either.


  2. #2
    That is true Polaris usually only makes 2 over sizes. .25MM and .50MM. I bet you have WSM pistons which are just like OEM and you should be able to just use them to replace that one bad one. Ask a WSM dealer if that Piston has the same markings on it. Did you measure to make sure it is .75MM over?

  3. #3

    Join Date
    Jul 2008
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    England.Great Britain . UK
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    hi m8 look at WSM pistons usally std . 025/ .050/ . 075 / . 100
    seen other makes . 150

    some after market pistons better than oem

    google wsm pistons

  4. #4

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    Sep 2009
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    Picture

    Has anyone seen a 78A on any brand of piston besides OEM Polaris. WSM, Wiseco, ? Looked at this closer today and it is definately a 0.75 oversize which dealer tells me Polaris did not make.
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  5. #5
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    That's a WSM piston, it looks identical to OEM.

    Also the head gasket is WSM, which was the give away for me.

  6. #6

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    Piston

    Quote Originally Posted by xlint89 View Post
    That's a WSM piston, it looks identical to OEM.

    Also the head gasket is WSM, which was the give away for me.
    Thanks Kevin, Well that is good news. Now I can buy a matching piston to the others. What was the give away on the head gasket? I always thought that only Polaris OEM pistons had the 78A on them.

  7. #7
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Yeah, I used to think that too.

    Then I got some WSM pistons and they have the same marks.

    The WSM gaskets have the tabs that are riveted together. Stock and Cometic are riveted together at the water jackets openings.

    FYI: they claim the WSM are stock OEM replacements. Suppose to be able to interchange the rings, pins, and circlips between the 2.

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