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Oversized valves to fit a Seca 550

Discussion in 'XJ Modifications' started by justind97, Dec 23, 2014.

  1. justind97

    justind97 New Member

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    Hey guys,

    New to the forum. I've been racing an 82 Seca 550 in some vintage races.

    The motor I have had been heavily modified, but I don't think the valves have been oversized yet. On a CB550, oversized valves can be good for up to 8hp on some motors.

    So my question is, is there oversized valves made for a 550? Looking for +1mm. If not, do the valves from another motor fit with no modifications?

    Thanks!
     
    justind97, Dec 23, 2014
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    Thrasher likes this.
  2. Thrasher

    Thrasher Member

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    Try the head from the FJ600.
    What has been done to your motor?
     
    Thrasher, Dec 23, 2014
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  3. zombiehouse

    zombiehouse Member

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    Look at the head for an FZ600 too.
     
    zombiehouse, Dec 23, 2014
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  4. Thrasher

    Thrasher Member

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    Or the YX600 Radian.
     
    Thrasher, Dec 23, 2014
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  5. Polock

    Polock Well-Known Member

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    If you putting valves in, change the guides cut the seats and use any valve within reason
     
    Polock, Dec 24, 2014
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  6. justind97

    justind97 New Member

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    Within reason, yes. I'd ideally like to go +1mm, but what I can't seem to determine is what motor will be closest to that and fit with little to no modifications.


    The head has been extensively ported and polished with a decreasing radius from outside to inside to help the Venturi effect and increase velocity.
    It was done by an ex pro bike engine builder from Toronto I believe.
     
    justind97, Dec 28, 2014
    #6
  7. Polock

    Polock Well-Known Member

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    little to no modifications = the valves you have now
    take a look here, it's not your engine but the ideas are the same
    http://www.aperaceparts.com/cope.html
    then get to know someone with a dyno
     
    Polock, Dec 28, 2014
    #7

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