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XJ700x heads vs XJ750X heads

Discussion in 'XJ Technical Chat' started by nkavanau, Oct 22, 2009.

  1. nkavanau

    nkavanau Member

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    Can the XJ700x heads be used on the XJ750x motor? I know the bore and stroke are different, but not sure about the heads. Want to rebuild a spare one to keep on hand and the 750's are a little harder to find.
     
    nkavanau, Oct 22, 2009
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  2. schmuckaholic

    schmuckaholic Well-Known Member

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    I believe, and the Maxim-X site seems to confirm, that the bore is the same between the two; the difference lies in the stroke.

    I'd confirm this with HAP first, but to the best of my knowledge, the head should interchange between the two engines.
     
    schmuckaholic, Oct 22, 2009
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  3. JoeFriday77

    JoeFriday77 Member

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    My understanding is the same. They just changed the cc rating with the stroke.
     
    JoeFriday77, Oct 23, 2009
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  4. littlegiant

    littlegiant Member

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    Intersting and GOOD to KNOW.
     
    littlegiant, Oct 23, 2009
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  5. nkavanau

    nkavanau Member

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    Thanks guys. You are correct on the bore, they are both he same.
    XJ750X Bore x Stroke: 68.0 x 51.6 mm
    XJ700X Bore x Stroke: 68.0 x 48.0 mm
    With the lack of 750 parts, that's one less thig to worry about.
    So it looks like the only difference between the two blocks is the con rod length, and carb jets. Sound right?
     
    nkavanau, Oct 25, 2009
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  6. JoeFriday77

    JoeFriday77 Member

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    That matches my understanding between the two.
     
    JoeFriday77, Oct 25, 2009
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  7. nkavanau

    nkavanau Member

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    OK, now I think I made an error on that assumption. Wouldn't it be the crankshaft that dictates the stroke, and not the con rods?
    Wouldn't it make sense that no matter what length con rods are put on, the stroke could never be greater or less than the travel of the con rod journal from BDC to TDC?? So if that stands true, wouldn't the 700X and 750X have to be using different cranks??
    Just thinking independently, something the wife says I shouldn't do..
     
    nkavanau, Oct 28, 2009
    #7

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