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Thread: Tuning carbs...

  1. #1
    Almond's Avatar
    Join Date
    Jul 2006
    Moscow, Russia

    Tuning carbs...

    There is an idea to tune low jets for each cylinder separetely.

    In other words, I unplug spark plugs wires for two cylinders but leave third in place. Theoretically engine have to work with only one cylinder connected to ignition. But it startsm very unstable at idle and dies after pulling throttle. If I use primer at this time engine work.
    Does it men it is lean?
    I've made a decision to try this method because it seems that there is not enough acceleration from idle to mid RPMs - it is very important for CC race. At the same time here is perfect acceleration from 4500 RPMs to WOT (7700)...
    I hve too much mods on my ski, shortly I use Novis and FP triples...

    And one question to Novi gurus:
    I have pressure gauge installed in return line. The measurements are 1,5 at idle but 8,5 at WOT! I've read Novi recommendations, they say that only 5-6 is normal at WOT. What is your experience? Are them right and I need to increase the size of jet in return line or I can leave this jet (90) in place?


  2. #2
    spdracr's Avatar
    Join Date
    Sep 2005
    Fort Lauderdale
    for the return jet on my stock carbs I am running a 100.
    On my big bore with novi's I'm using a 120. If I remember there is a diagram of how to install Novi's and it has Tim's recommendations on what pressure you need.

  3. #3

  4. #4
    if you try and tune each cylidner differently ie one at a time
    then what about the extra load the engine is under when you are tunning

    the jetting will be different as its trying to drag the other cylinders over
    when all the cylinders are firing together it will need less fuel

  5. #5
    txgp1300r's Avatar
    Join Date
    Apr 2006
    Dallas , Texas
    Yes ..not to mention the empending GIANT backfire from all the unburned fumes in the sound suppresion box.....b.t.d.t.........split muffler,burned foam,hosed blown off,turd in shorts,black soot everywhere.etc

  6. #6
    What jetting are you running??? Manifold??? Cages???

  7. #7
    Almond's Avatar
    Join Date
    Jul 2006
    Moscow, Russia
    Thanks all...



    Needle and seat 2.3
    Spring 95 gram
    Pop-off 20
    Pilot Jet – 150
    Main Jet – 175
    Restrictor jet in return line - 90.

    VForce3, FPTriples, 130psi compression, 92-93 octane pump gas, ported cylinders, Novi carbs, air filters WITHOUT prefilters -I have tried them covered with prefilters, there is no noticable difference, fuel mixture become slightly richer.

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