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  1. #1

    How bad to use A size piston is B cylinder?

    could I use a A size pro x piston in a B cylinder? How bad would it be??? 2001 GP1200R.


  2. #2
    WATER WOODY's Avatar
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    What number is on the cylinder?

  3. #3
    Moderator beerdart's Avatar
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    They are sized for a reason.

  4. #4
    I believe either 7 or 8 I just ask because some kits dont even do different sizes.

  5. #5
    snowrunner's Avatar
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    If it's a stock cyl, it doesn't matter unless your looking for the absolute most you can get out of you motor. The size differences are in microns, it won't matter - did it on my 1200R and still runs like a top.

    Call Island Racing or Group K, they'll confirm this (they told me that bit of info in the first place).

  6. #6
    Moderator Insanediego Joe's Avatar
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    Quote Originally Posted by snowrunner View Post
    If it's a stock cyl, it doesn't matter unless your looking for the absolute most you can get out of you motor. The size differences are in microns, it won't matter - did it on my 1200R and still runs like a top.

    Call Island Racing or Group K, they'll confirm this (they told me that bit of info in the first place).
    snow is correct. It really wont matter from an A to a B....

  7. #7
    Moderator RX951's Avatar
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    my number 1 and 3 have 1 size smaller pistons than what the cylinder stamping calls for been running like this for 4+ years.

    The difference is so small.

    I am not recommending it, but letting you know it has not hurt my engine at all.

    OEM GP1200R

    Red: 79.899 ~ 79.902 (3.1456 ~ 3.1457)
    Orange: 79.903 ~ 79.906 (3.1458 ~ 3.1459)
    Green: 79.907 ~ 79.910 (3.1459 ~ 3.1461)
    Purple: 79.911 ~ 79.914 (3.1461 ~ 3.1462)

    1-5 cylinder gets an A piston
    6-10 cylinders gets a B piston
    11-15 cylinders gets a C piston
    16-20 cylinders gets a D piston

  8. #8
    another question can I reuse the cylinder base gasket and exhaust manifold gasket they have about 45 minutes on them I am hoping when I go to take them off they come off easy and can just reuse them. Anyone do this?

  9. #9
    WATER WOODY's Avatar
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    Quote Originally Posted by RX951 View Post
    my number 1 and 3 have 1 size smaller pistons than what the cylinder stamping calls for been running like this for 4+ years.

    The difference is so small.

    I am not recommending it, but letting you know it has not hurt my engine at all.

    OEM GP1200R

    Red: 79.899 ~ 79.902 (3.1456 ~ 3.1457)
    Orange: 79.903 ~ 79.906 (3.1458 ~ 3.1459)
    Green: 79.907 ~ 79.910 (3.1459 ~ 3.1461)
    Purple: 79.911 ~ 79.914 (3.1461 ~ 3.1462)

    1-5 cylinder gets an A piston
    6-10 cylinders gets a B piston
    11-15 cylinders gets a C piston
    16-20 cylinders gets a D piston
    Iva always ran a smaller piston in #3 on my 1200's,never a problem

  10. #10
    Moderator RX951's Avatar
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    exhaust manifold gaskets I haev reused. But base gaskets IMHO are too risky to reuse. I would use a new base gasket. You don't want to chance any leaks.

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