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XJ900F capacity increase?

Discussion in 'XJ Modifications' started by wrecker, Dec 5, 2021.

  1. wrecker

    wrecker New Member

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    Is it practical to increase the Capacity of the XJ900f engine. ?
     
    wrecker, Dec 5, 2021
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  2. Simmy

    Simmy Well-Known Member

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    There was an 853 cc and an 891.
    67 mm bore became 68.5 bore.
    Stroke was 60.5 for both.
    An 853 could be converted to an 891.
    I'm unaware of anyone enlarging an 891 beyond the Yamaha slight bore increases offered for rebuilding purposes,
    these overbore piston & rings are likely difficult to source today.
    The XJ900 developed the reputation as a simple & dependable ride and was no longer considered a performance bike.
    Likely why performance parts are not common today.
    Is it practical? Hot rodding never is.
    Is it fun and challenging? You bet!
     
    Last edited: Dec 13, 2021
    Simmy, Dec 13, 2021
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  3. Minimutly

    Minimutly Well-Known Member

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    Unless the 853 is worn, is it worth it? If you have the bits cheap or for little cost yes, maybe. As for gaining performance?
    It’s been stretched from 650 anyway - surely the better way would be a different motor, or maybe gas flowing head and valves, 4 into 1, flat slides?
     
    Minimutly, Dec 13, 2021
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