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  1. #11
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    Re: 200psi in js500!!

    Yeh 116mm on the dot, I've measured the head from the centre line at its highest point ( not the bolt holes ) and with the guages in at the side from the centre it reads 34.5mm? If that makes sense where I've measured it from?

  2. #12
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: 200psi in js500!!

    That being the case... With stock thickness head and base gaskets I would typically run 22cc domes with 93octane gas (not sure what the 93 octane equivalent is in Europe, 95 or 96 maybe?). It is impossible to guess your current dome volume by measuring your head casting height at this point since the head has been re-chambered. Also it was (and still is) pretty common to just mill the undercut off a stock head to boost compression or you can install a thinner head gasket. Both options will keep you in the safety zone with premium pump gas.



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  3. #13
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    Re: 200psi in js500!!

    Thinnner or thicker gasket? I'm confused? I'm going to try get a stock cylinder head for starters and take things from there I think this ones just guna cause a head ache and yeh it's 95 or 97 octane here

  4. #14

    Re: 200psi in js500!!

    Stock head with stock thin gasket. OEM metal gasket is .08" I think.

  5. #15
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    Re: 200psi in js500!!

    Quote Originally Posted by 2strokesmoke View Post
    Stock head with stock thin gasket. OEM metal gasket is .08" I think.


    So I want to to go for a metal one or the fibre one? It's had fibre ones on before but if metal ones are better I'll use that

  6. #16
    I dream skis E350's Avatar
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    Re: 200psi in js500!!

    Question, but related to original topic. Our '93 550sx is 184 psi in each cylinder and I am running ~98 octane (.75 gal 110 race gas plus 4.25 gal 91 octane pump gas).

    If I or the OP were willing to run the appropriate blend of race gas and pump gas to prevent pre-ignition, what would the performance change (increase?) be? In other words,

    Would it have more torque at low rpm?

    Would it have more torque at all rpms?

    Would it have a higher max rpm?

    P.S. Dutchyboyyyy from England. I pay $9.65 per gallon for 110 race gas which is likely what you pay for regular pump gas in England.
    Last edited by E350; 07-27-2017 at 05:13 PM.

  7. #17
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    Re: 200psi in js500!!

    in europe, our fuel unleaded 98RON(research octane number), and 87MON(motor octane number) make exactly 92.5 aki (RON+MON/2) .... AKI is the us norm isn"t it???? in europe the octane number write on the pump is the RON, for the us , is the aki number

  8. #18
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: 200psi in js500!!

    Stock Kawasaki PP 550 gasket thickness is .045", most AM fiber gaskets that come in the kits are .040".

    A .020" thick copper head gasket is the one I would use with an unmolested stock head and premium pump gas. Advancing ignition timing 3 degrees from the stock setting is also safe with the above set-up and it will provide a noticeable improvement to low rpm and midrange performance.

    Quote Originally Posted by Dutchyboyyyy View Post
    So I want to to go for a metal one or the fibre one? It's had fibre ones on before but if metal ones are better I'll use that



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  9. #19
    PWCToday.com Is My Home Away From Home mcn6's Avatar
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    Re: 200psi in js500!!

    Blending .75gl 110 + 4.25gl 91 = 93.85 octane.

    Increased compression = Increased low rpm and midrange torque. You will see a small increase in upper rpm performance and max rpm, but not much.

    Quote Originally Posted by E350 View Post
    Question, but related to original topic. Our '93 550sx is 184 psi in each cylinder and I am running ~98 octane (.75 gal 110 race gas plus 4.25 gal 91 octane pump gas).

    If I or the OP were willing to run the appropriate blend of race gas and pump gas to prevent pre-ignition, what would the performance change (increase?) be? In other words,

    Would it have more torque at low rpm?

    Would it have more torque at all rpms?

    Would it have a higher max rpm?

    P.S. Dutchyboyyyy from England. I pay $9.65 per gallon for 110 race gas which is likely what you pay for regular pump gas in England.



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  10. #20
    PWCToday.com Is My Home Away From Home freekstyle's Avatar
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    Re: 200psi in js500!!

    You are not living unles you run 220+ lbs! Your crank will tell you otherwise, but why listen to that? Who isn't up to an engine build after 2 motos and practice? Larry entincer would just hold her wide and send it!
    Last edited by freekstyle; 07-28-2017 at 01:09 AM.

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