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Overbore question

Discussion in 'XJ Technical Chat' started by kerriskandiesinc, Nov 3, 2019.

  1. kerriskandiesinc

    kerriskandiesinc Active Member

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    Just curious, on the 750 range, does the maximum overbore allowed, create the '853cc' size of the ( early ) 900....I know the later one was stroked too....anyone any ideas??
     
  2. XJ550H

    XJ550H Well-Known Member Premium Member

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    there were kits for this but it requires you to bore out over maxim spec
    piston750.PNG piston750.PNG
     
    Last edited: Nov 3, 2019
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  3. cds1984

    cds1984 Active Member

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  4. Timbox

    Timbox Well-Known Member

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  5. kerriskandiesinc

    kerriskandiesinc Active Member

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    That isn a bad price at all...especially if you already have a somewhat tired, low compression motor....Wonder how much extra umph you'd likely get though, with 'only' 818cc.....

    Maybe another 4-5Lbs of torque ( always useful) .....maybe 4HP??
     
  6. Ryengoth

    Ryengoth Active Member

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    I would never overbore an airhead due to possible wall warping. That little bit of extra "upmh" could quickly turn into a new upper half. If you have a spare head and piston set go for it and put it on a dyno to record the difference.
     
  7. XJ550H

    XJ550H Well-Known Member Premium Member

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    I would think you would have to change the jets some. just think of the different jets between 650 and 750
     
  8. Timbox

    Timbox Well-Known Member

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    I love the XJ's but I think if I was was going to go with a big bore kit I would be going with a 1000 or 1100 model that was more designed for it. Love how these bikes work stock, if I wanted more power hp/torque I think I would find another bike.
     
  9. cds1984

    cds1984 Active Member

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    No change to jets or carbs for 748cc to 818cc with that kit.
    Might help something, but the low end power was what I was after.
    Worked a charm.
     

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