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  1. #1

    Piston to wall clearance? I have no spec.

    Installing new .20 over WSM pistons in my 2007 215 engine. The pistons came with a warning slip about the oil squirter but nothing about wall clearance.
    I have the case at the machine shop now and need to tell them the tolerance.
    Anyone know?


  2. #2
    ncdoo's Avatar
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    OEM is .0015, I'm not sure about WSM pistons. Normally they give you the recommended clearance along with the piston.

  3. #3
    Derek45's Avatar
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    I was always under the impression If a cylinder is over 0.020mm or ????mm then the pistons are always smaller to acomadate the ring gap/clearance

  4. #4
    It will depend on the Alloy used to make the piston you bought.. every piston mfger has a different Alloy. SEADOO OEM spec piston skirt clearence is tight.(MAHL MOTORSPORTS BUILT) for Seadoo.. But they have a low expansion type piston ALLOY if your not Sure? Call the piston Mfger.. I just setup a set of Wisco pistons in a 04 215HP at .002 skirt clearence & check all your top & middle ring gaps in the finished cyl before you assembly it.

  5. #5
    WSM said to use the manufacturer spec but I am uncomfortable with that. I was told by a member here to use .004

  6. #6
    Should I do ring gaps at manufacture spec?

  7. #7
    Called WSM and they said .0045-.0050

  8. #8
    Nothin' better than Doo'in it! BigDaddyRXP's Avatar
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    That's loose!

  9. #9
    ncdoo's Avatar
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    WTF?? Anyway OEM pistons have a big taper from the shirt to the piston tops, thats why they recommend the tight clearance, .0015".


    Quote Originally Posted by Derek45 View Post
    I was always under the impression If a cylinder is over 0.020mm or ????mm then the pistons are always smaller to acomadate the ring gap/clearance

  10. #10
    Quote Originally Posted by pjv911 View Post
    Called WSM and they said .0045-.0050
    If you must guess? I would set them up at .003. 004 - .005 is too loose for a forged piston for that bore size..

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