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highly modded 650 Seca

Discussion in 'XJ Modifications' started by Simmy, Mar 25, 2016.

  1. Simmy

    Simmy Well-Known Member

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    Absolutely, that’s what is important, as you already said different dynos on different days give varying results. People need to realize hp delivered at the rear wheel is much less than sales literature at the crankshaft. Air pressure in the rear tire will affect results.
     
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  2. MattiThundrrr

    MattiThundrrr Not a guru

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    Horsepower is only a result of a mathematical equation (for the nerds out there, here it is. [RPM * T] / 5252=HP, where RPM is the engine speed, T is the torque, and 5,252 is radians per second. That 5252 denominator is the reason every horsepower graph crosses the torque line at 5252 rpm) Torque is all that really matters, and the space under the torque curve is what shows you what an engine can do. A wide, smooth torque curve makes a useful, powerful engine. Peaks and valleys are not your friend.
     
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  3. JeffK

    JeffK Well-Known Member

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    I can't debate Matt's math because he's correct.....but I will be happy to put my '75 H1 up against any non-turbo XJ 750cc or less to show that peak HP is sometimes very, very good if you know how to keep it in the powerband.....the little 500cc green one there in front.....one very badass bike! I didn't spend much time with the appearance as the jewel in this build is the engine was a test-bed that combined several porting mods that worked so well together, it's never been taken apart since.

    For the masses though, of course you're right....us 2 stroke guys are an anomaly today....

    jeff
     

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  4. Simmy

    Simmy Well-Known Member

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    I noticed my final drive started leaking oil so I pulled the drain plug to see how much oil was still there.
    Still lots of oil but I found a spring clip from one of the oil seals stuck to the magnet on the drain plug.
    Rather than begin repairing it I just replaced it with a spare unit I had on hand.
    Finish is not up to the standard so that's work for another day. The black does look better
    IMG_2246.jpg
    IMG_2243.jpg
    IMG_2245.jpg
     
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  5. Minimutly

    Minimutly Well-Known Member

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    Hi, stupid question time. To do this conversion needs a 750x head, fzr 1000 block? Could these go on a xj900f bottom end? Is there another genesis engine with horizontal carbs?
     
  6. Minimutly

    Minimutly Well-Known Member

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    The point of the question is that firstly 750x heads are scarce around here. And I'm wondering if this lot will fit in my 900f project frame.
    Maybe I could fabricate or rather modify the 1000 inlets inlets to make the carbs horizontal?
     
  7. faffi

    faffi Active Member

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    Apart from better engine temp control, and likely more top end power, what are the primary benefits of the X engine over using a 900 Seca engine?
     
  8. Simmy

    Simmy Well-Known Member

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    Interesting question, combining the FZR1000 bore with the XJ900 stroke would make 1069 cc.
    The 1st thing that comes to mind is the water pump. The X has this driven off the clutch basket/shaft.
    You would need to use an electronic pump. A quick perusal of the auto world here https://www.summitracing.com/search/part-type/water-pumps-electrical
    a lot of these pumps are 10A so that wouldn't work but I did see one at 6A, still a lot for the puny output of our XJ's. Hiding it might be difficult.

    Things I don't know - are the wrist pins for the Genesis same diameter as the XJ's?
    The stroke is only increasing by 4.5 mm (XJ900 60.5 Vs FZR1000 56) so the pistons are only poking into the barrels 1/2 this, you might need a shim at the base gasket.

    The 700X/750X is the only one.

    I could source a head for you that's not a problem, I believe the heads of the 700X and 750X are the same.
    As far as I know Canada is the only market for the 750X but they are really common here.
    To get my 911X motor into the 650 Seca frame I have to remove the valve cover, then there is just enough clearance.
    I'm uncertain if the 900 frame gives you anymore room.

    You said it - more top end power!
    The 900 redlines at 9500
    700X at 10,000
    750X and FZRs 11,000
    higher compression to.
     
  9. faffi

    faffi Active Member

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    Perhaps you could use the idea of Roland Eckert? When making a street legal race bike based on the CB900/1100F engine, finding the alternator making the engine too wide, he moved the alternator further back and drove it via belt https://www.motorrad-fuchs.com/en/single,979,,Eckert_RE1.html

    Somewhere on the XJ900 engine, there should be a rotating point to power a water pump. Cam shaft, for instance, for which I know there are pumps for other applications. If it is worth the effort is another question.
     

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