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Thread: 90 mm pistons

  1. #1
    OLD # 7 IEGPR's Avatar
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    90 mm pistons

    I was just wondering if anybody has a motor with 90mm pistons. If so what heads are you using??


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    philip_gpr's Avatar
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    OEM GP1200R with a little bit of machining

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    ou812's Avatar
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    Quote Originally Posted by IEGPR View Post
    I was just wondering if anybody has a motor with 90mm pistons. If so what heads are you using??
    You trying to CC up for the bug are ya?

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    OLD # 7 IEGPR's Avatar
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    Just tryen to fig out what I want to do. It seems to me that when people start going big bore they disable the powervalves. With my 06 thats one step I can skip. and if Im going to bore it, its gona be BIG.

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    OLD # 7 IEGPR's Avatar
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    Quote Originally Posted by philip_gpr View Post
    OEM GP1200R with a little bit of machining

    What do you think of a OEM 1300 head with a little bit of machining??

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    philip_gpr's Avatar
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    I think you should use the head that matches the cylinders you use.

    With either head (1200 or 1300) the 1300 gasket tends to seal better - use the 2005 GP1300R head gasket.

    with these big motors power valves are not needed

    The 3 different cylinder choices have different port timing - that is the more complex issue that has to be decided
    Last edited by philip_gpr; 12-09-2007 at 10:16 PM.

  7. #7
    OLD # 7 IEGPR's Avatar
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    Quote Originally Posted by philip_gpr View Post
    I think you should use the head that matches the cylinders you use.

    With either head (1200 or 1300) the 1300 gasket tends to seal better - use the 2005 GP1300R head gasket.

    with these big motors power valves are not needed

    The 3 different cylinder choices have different port timing - that is the more complex issue that has to be decided

    THANKS PHILIP

  8. #8

    Billet heads for 90mm

    We make billet heads that will support up to 90mm. We can sell them in sets of three for $525 or $650 with girdle hardware. Here is a link https://www.waterdawgkustomz.com/pro...?prod=GPBB-BHK


    Jeff

  9. #9
    OLD # 7 IEGPR's Avatar
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    Cool Jeff, Thanks

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    Moderator OsideBill's Avatar
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    Quote Originally Posted by IEGPR View Post
    Just tryen to fig out what I want to do. It seems to me that when people start going big bore they disable the powervalves. With my 06 thats one step I can skip. and if Im going to bore it, its gona be BIG.
    I kept my powervalves intact on my 1390 build many people have. The groupK motors were the ones that pinned them open. Talk to your motor builder about this.

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