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How many turns out @ idle are you ?

Discussion in 'XJ Technical Chat' started by Knick, Jun 30, 2006.

  1. Knick

    Knick Member

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    *disclaimer, I haven't tuned with Yics or colortune yet* Seca 750

    I have heard you should be 2.5 or so turns out to get a good mix at idle..

    Using a single port vacuum (no yics), and rpm to set it I am at 5 or so turn, and the plugs are still light (probly need 1/2 to 1 turn)

    This is with a stock air box, filter and the exhaust is a 4 into 2 (looks aftermarket since it doesnt have any crossover type bracket under the tranny)

    So... back to the question..

    6 turns seems like the idle is having to make up for jets being too small..

    I also notice the 4500+ RPM pinging, possibly from CCT or just a lean condition.. (87 oct)

    I had planned to upgrade to a K&N (says retune, not rejet) but thinkin that might be enough to push me farther lean.

    THoughts ? (probly be a while before I can rejet, or mod..
     
  2. Knick

    Knick Member

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    PS: part of my "rejet" thought is based on an article i read on another site saying one size up normally results in say a 50% chagne in turns needed for idle.. (something like that at least)
     
  3. BlueMaxim

    BlueMaxim Active Member

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    I don't understand your single vacuum statement. You can't tune the carbs pilot mixture setting with a manometer. That can only be done with an exhaust gas analyzer or colortune plug. That said , here is some advice.

    What have you done to the carbs? Have you cleaned them at all, do you know the po (previous owner) and can ask him if he has done anything to the carbs. The 2.5 setting is a factory recommended starting point for tuning clean carbs. If the carbs are clean the setting should not vary but about +or- one turn. Trouble getting fuel at several turns out is indicative of dirty carbs or a fuel restriction. If the bike has sat up for a while the carbs tend to gum up and will have to be cleaned. The float level could also be low or a fuel filter could be clogged causing a restriction.
    I noticed you are in Austin Texas. We have some members there who might be willing to help you. Let me knwo how things go and if you want I'll contact them for you.
     
  4. Hired_Goon

    Hired_Goon Member

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    Rule of thumb is if you have to turn your mixture screw out more than four turns then you may need to go down one size pilot jet.


    If you think about how the mixture screw works with it'sconical or pointed end, the more you screw it out the less effective the adjustment is. Eg the clearance between the needle and housing changes less.

    Remember, the more turns out the leaner it gets.
     
  5. jdrich48

    jdrich48 Member

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    I think you got turned around there Hired_Goon

    The more you turn it out the richer the mixture gets. :)
     
  6. NACHOMAN

    NACHOMAN Member

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    Not sure on Hitachi carbs, But on Mikunis the pilot screw in inaffectual past 3 turns from seat. Granted, different carbs, different abilities, but twice the recommended setting, and still lean, is a bad sign. First thing I would do is pull the carbs doing a FULL cleaning incluging carb soak, and compressed air blowout, while fully disassembled. I would also replace the gaskets, float valves, throttle shaft seals and pilot screw orings (they are small and spring loaded so be careful). Resetting the float levels, isn't hard, but necessary with new valves. Then reset all the pilots to 2.5 turns from lightly seated. Overtightening the pilot screws will deform the seat (aluminum) and possibly the needle, making tuning dificult if not impossible. With all the pilots reset, synch with the appropriate tool, and you will be "on the paper". This should get you running well enough to find someone with a color tune or order one.

    With your pilot screws that far out, either someone has screwed with the jets (possible), or you are getting air in from some bad seals (more likely). Now would also be a good time to check the manifolds for cracking. They are usually shot by now.

    Hope this helps.
     

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