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Thread: Cracked Head

  1. #1

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    Hi Guys, Have just pulled the head off of my 84' GPz1100 thats out to 1500cc and have found that the head has split from the 6mm bolt on the right side of the head to the second spark plug hole and across the two plug holes on the left of the head am running 0.024 fuel jets and 0.022 N2O jets it ran a best of 8.46@150mph my question is have you guys seen this before and if you have what caused it ????? I would of thought that @ this level that this would of caused no problems with a A3 head Specs are<div></div><div>1984 GPz 1500cc</div><div>A3 head with 39mm in and 33ex and ported</div><div>44mm Lectrons with PJ</div><div>MTC Block and pistons @13.5:1</div><div>NOS Cheater Solinoids with Fogger Nozzles</div><div>NOS Launcher progressive controller</div><div>Dyna ignition and retard controller</div><div>30# timing with 6# removed over nos ramp</div><div>any propperadvice would be good </div><div>Thanks</div><div></div>

  2. #2
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    I am sure someone will chime in but Kawasaki heads cracking is common. They crack end to end.<div></div><div>Back when this bike was common they would weld aluminum supports between the cam towers to prevent the cracking. I believe even normally aspirated ones would crack.</div>

  3. #3
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    And I'll bet Paul Gast or Kim Barringer can fix it!!! Ray.
    GOD rides a SUZUKI!

  4. #4
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    Dont waste any more money mate get a vortex head on it

    <DIV>Geoff</DIV>

  5. #5
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    the trick is to get it welded on the ends before a crack starts (Pup lessons)
    street cars kill bike racers

  6. #6
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    All of this was done to prevent cracking back when stock heads were the only thing available.<div></div><div>Now there are already stronger aftermarket heads easily available.</div><div></div><div>They used to weld in between all the fins on the ends solid. Same time weld supports between the cam towers and on the inside of the bend outside ports on 2 and 3,since porting to staighten the port would break through.</div>

  7. #7
    Senior Member riceburner's Avatar
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    I never broke a KZ head like you are talking about, the only time I broke head was when I spit a valve shim.

  8. #8
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    Wasn't the Z-1/KZ head stronger than the later GPZ ones?<div></div><div>Anyway I don't even race a Z-1 but saw enough split heads from people that did.</div>

  9. #9

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    Thanks Guys all very interesting, when the bank balance allows i will be getting a Vortex but for the short term will have to stick with the stock GPz head and make it tough enough to take it. Unless some one out there has a second hand Vortex they want to sell.

  10. #10
    Senior Member riceburner's Avatar
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    No, the later GPZ/J model police bike 84 and later all have thick castings. Early KZ / Z1 had very thin combustion chambers. But then this subject has been beat to death --- think it maybe it time again for the dead horse?

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