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Help CVK Carb question?

Discussion in 'Kawasaki 250cc In-line 4's' started by Rossco_Perth, Feb 16, 2018.

  1. Rossco_Perth

    Rossco_Perth Confirmed Tinkerer :)

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    Hi All,

    Can someone please shed some light on the symptoms of blocked main air jets on CVK Carbs?

    (The AIR jet I'm talking about is the bass one that feeds air to the main needle from the lower centre of the front face of the carb)
     
  2. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    What symptoms are you experiencing?

    Is this the jet you're referring to....

    Needle Jet.jpg
     
  3. Rossco_Perth

    Rossco_Perth Confirmed Tinkerer :)

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    Yep, that’s the one


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  4. Frankster

    Frankster Grey Pride...Adventure before Dementia Staff Member Premium Member Ride and Events Crew

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    If that jet is blocked or the needle is getting stuck then your bike should idle okay, but that's about it. That jet is connected to the emulsion tube and main jet. If the emulsion tube can't aerate/atomise the fuel properly, then you'll experience rough running and that cylinder will probably be colder due to poor combustion. That "circuit" is different to the idle circuit, so if you have a rough idle, then your issue might be elsewhere. The Idle and Main jet circuits only overlap when you rev the bike and when the revs are coming down to idle. Make sure the jet and inlets (arrowed in the image) are all clean and unobstructed.
    Jets.jpg
     
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  5. Rossco_Perth

    Rossco_Perth Confirmed Tinkerer :)

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    Thanks for that, the symptoms I had were Ritch midrange throttle that cleared up above 3/4 throttle.
    This was on a 1992 ZZR600 that I picked up cheap ($1300 with rego).

    It was running like a dog down low & in the mid range but came on song above 3/4 throttle & over 7k rpm.

    Long story short is that I pulled the carbs off it Friday & found that 1 carb was missing the idle pilot screw completely (wtf?)
    Good news is that the cvk 36’s on the zzr600 use the same idle needle as the cvk30’s on the ZXR so I stripped & rebuilt the carbs, unclogged the main air jets, replaced the missing idle needle & now she is mint!


    f0f996ec291a203ea840592d05ceab89.jpg


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  6. banner001

    banner001 Well-Known Member Premium Member Contributing Member

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    A blocked main air jet will give you symptoms of running rich, like a much bigger main jet, it will also make the throttle response a tad bit worse when on a cold engine due to the less-atomised fuel.

    It's fairly common on race engines to block off the air jets when running a custom ram-air intake.
     

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