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Thread: Bore on Cyl?

  1. #1

    Bore on Cyl?

    Hi everyone,

    This seems like a silly question but here goes, can you bore out only one cyl on a sl750? Only one cyl is bad, the other two are still in good shape. If only one jug was oversized would it create a vibration or imbalence in the engine?
    Any thoughts?


  2. #2
    I'm addicted to Polaris PWC ghostinstallations's Avatar
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    Its not a silly question, just one that has been answered several times. The search function can offer many great results. In short, the cyls' dont need to match, but it is reccomended to have matching size pistions if you can. I would not go more than one size over before replacing all three.

  3. #3
    Thanks for the info. I'm starting the engine tear down now as to determine how much i'm into this this for. The old pistons are marked W7A 25. It looks like it was already bored out .25mm. I'm wondering if anyone would know the brand of pistons by these numbers? Two of the cylinders are in good shape and would like to get the proper rings to match the pistons after honing.

  4. #4
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Most likely stock or WSM brand.

    You can swap WSM brand parts with OEM and they are cheaper to buy. (most of us run them).

  5. #5
    Thanks for the info. One more question, i will be ordering pistons before I have the cyl bored but i'm wondering how make sure i have the correct piston to cyl clearence. When i order the 70.25mm pistons do they come a touch smaller for clearence or are the cyliners bored out to just over 70.25?

  6. #6
    She likes the bike. But the ski gets her wet!!!! xlint89's Avatar
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    Have the cyls inspected FIRST. Then the machine shop can decide what size pistons to get. But the cyls should be bored to each specific piston. (matched set of piston to cyl)

  7. #7

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    yes generally pistons are slightly smaller than the finish bore size. clearance is built into the piston. But as stated, pistons should be mic'd and matched to each cylinder

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