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TO MUCH FUELL ON THE PLUGS 618

in 2 Stroke Technical Questions 13 years ago

  • Re: TO MUCH FUELL ON THE PLUGS 618

    by » 13 years ago

    Yanis,

    Can you shorten the adjustment at the throttle? That would raise both slides, then you could lower the high one with carb adjustment.

    Bill.
      
    Report

  • Re: TO MUCH FUELL ON THE PLUGS 618

    by » 13 years ago

    BILL THAT IS BRILLIANT!!!!!
    Thank you,
    I will report as soon as I look things over,
    Yanis
      
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  • Re: TO MUCH FUELL ON THE PLUGS 618

    by » 13 years ago

    Yanis I have copied these instructions off a yahoo web site....they are written by a guy that taught me a lot about 2 stroke and they work for me....I still have a lot to learn....

    It maybe worth reading what Bob say in them and starting with a clean sheet of paper,

    ----------------------------------------------------------------------------------------------------

    From Bob Metzler
    Check for water or crap in the carb bowls. Make sure carbs are mounted
    square with the engine since a tilted carb can cause one cylinder to run
    hotter than the other on some engines. Cracks in the carb mounting
    sockets can cause lean mixtures so replace them if they are brittle.
    Check for adaquate fuel flow to the carbs. Any time you notice higher
    than normal EGT or if the plane won't reach normal full throttle RPM
    install a new fuel filter before you waste a lot of time looking for other
    problems. See my article on fuel systems for more info.

    Each carb has an idle jet, a needle jet with a jet needle and a main jet.
    All have tiny numbers on them which tell you the size. Check to be sure
    they are the factory recommended jets and the jets are the same in both
    carbs because its common to find that a previous owner has installed
    different jets. The factory recomendations are almost never wrong so
    its very important that the factory jets are used during testing.

    Check that all throttle cables are routed to drain out any water inside the
    cable outer jacket. Water collecting in a low spot can cause corrosion
    or freeze in the winter to lock the cable in one position.

    CABLE ADJUSTMENT FOR A SINGLE CARB
    Pull the throttle all the way back against the lower throttle stop. Where
    the cable enters the top of the carb there is an adjustment that is covered
    by a rubber boot. Slide the rubber boot up the cable to get it out of the
    way then gently pull upwards on the outer jacket of the cable. There
    should be a tiny amount of free movement before you feel the inner cable
    start to move the slide upwards. That tiny amount of free play is critical to
    be sure that the cable is not holding the slide up off of the idle speed
    adjustment screw. If you have trouble feeling it you can remove the air
    filter and look inside the carb throat to watch the slide move. Loosen the
    lock nut and turn the adjustment screw until you have that tiny amount of
    free play if needed. Lock the adjustment and work the throttle back and
    forth a few times to be sure the cable outer jacket ends are fully seated
    in their sockets correctly then pull the throttle all the way back against the
    lower throttle stop. Double check that the amount of free play is still
    correct at the top of the carb before you reinstall the rubber boot.

    Push the throttle all the way forward against the upper throttle stop and
    look in the carb throat. The slide should go up far enough so that it does
    not block any of the carb throat opening. Its okay if it goes up just a little
    extra but if it goes up too much it will bind and put a strain on the throttle
    cable. You should install some sort of upper throttle stop to prevent that.


    CABLE ADJUSTMENT FOR DUAL CARBS
    Dual carbs must be mechanically matched or one cylinder will have a
    higher EGT than the other and/or you can not get a smooth idle. Pull the
    throttle back against the lower throttle stop. Where the cables enter the
    tops of the carbs there are adjustments that are covered by rubber boots.
    Slide both boots up the cables to get them out of the way. Loosen the
    locknuts and turn both adjusment screws down two turns. That makes
    sure that the cables are not holding the slides up off of the idle speed
    adjusting screws.

    Remove the air filters and use the smooth ends of drill bits as round
    feeler gages to check the clearance between the bottom of the slide and
    the bottom of the carb throat on each carb. Pick a drill bit that will barely
    slide into the smaller of the two openings and use it to adjust the idle
    speed screws on both carbs until both openings are the same. Your
    carbs are now mechanically matched. To keep them matched you must
    ALWAYS turn the idle speed screw on both carbs the same amount
    when makeing idle speed adjustments. NEVER adjust just one idle
    speed screw.

    Make sure the throttle is pulled all the way back then go back to the cable
    adjusters on top of the carbs. Screw them out to take out ALMOST all of
    the free play. You check that by feeling how much you can lift the outer
    jacket before you feel resistance. It takes a delicate touch but you need
    just a tiny amount of free play to make sure that the slides are not held up
    by the cables when the throttle is pulled all the way back. If the free play
    is not the same on both carbs then one slide will start to rise before the
    other so this adjustment is critical. Tighten the locknuts and work the
    throttle back and forth a few times to be sure that all the cable outer
    jacket ends are fully seated in their sockets correctly. Double check
    that the free play is still correct on both carbs then slide the rubber boots
    over the adjustments. If you have done it correctly both slides will start
    to move upwards at the same time and the bottom of both slides will be
    flush with the top of the carb throat just before you reach full throttle.

    Set the throttle wide open and check that both slides go up far enough
    so that they don't block any of the carb throat openings. Its okay if they
    go up just a little extra but if they go up too much they will bind and put
    a strain on the throttle cables. You should install some sort of upper
    throttle stop to prevent that.


    INITAL CARB ADJUSTMENTS
    Because the jet RPM ranges overlap you should make the idle speed
    adjustments first and work up to higher RPMs. If any large adjustments
    are made it will be necessary to repeat the idle adjustment procedure to
    fine tune all adjustments. Make sure a clean air filter is installed before
    makeing adjustments.

    There is an AIR MIXTURE adjustment screw which will fine tune the
    amount of air at idle speeds only. The IDLE SPEED screw limits how
    far the slide can come down to close off the air flow. If you aren't sure
    which screw is which you can see the end of the idle speed screw
    sticking out inside the carb air inlet if you remove the air filter. A spring
    above the slide pushes the slide down against that screw.

    To prevent engine shake and gearbox chatter our engines need an idle
    speed of around 2000 RPM so warm up the engine and adjust the idle
    speed screw for about 2000 RPM. Remember to turn BOTH idle speed
    screws the same amount to keep the carbs matched if the engine has
    dual carbs.

    Adjust each air mixture screw to get the highest RPM at that idle speed
    setting. 1/8 of a turn on adjustment screws can make a big difference so
    keep the adjustments small. You will have to go back and forth between
    dual carbs a couple of times to get the best possible idle because they
    interact.

    As the mixture gets better the idle speed will increase so adjust both idle
    speed screws the same amount then fine tune the mixture screws again.
    Keep at it until the engine idles smoothly at the lowest speed which has
    minimum engine shake. Check the cable adjuster on top of both carbs
    after you finish to make sure there is still the same tiny amount of free
    play on each carb.

    Be aware that it's easy to get an arm cut off by the prop and anything you
    drop may go through the prop. I usually tie a short safety rope around my
    waist and the base of the wing spars so that I have to stretch way out to
    reach the adjusting screws. That way I can't forget and move toward the
    prop. Fortunately you won't have to do this again until you notice an idle
    problem.

    ------------------------------------------------------------------------------------------------

    Hope you find it useful I did.

    Nick.
      
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  • Re: TO MUCH FUELL ON THE PLUGS 618

    by » 13 years ago

    Yanis,

    If you follow the instructions Nick posted, The carbs should be tuned perfectly. Based on on what you have said so far, I would check one thing first. Back the idle speed screws out and pull the throttle all the way off. The slide should go all the way to the bottom. Then push the throttle to full and the slide should open completely. If you don't have that full travel, adjust the cables until you do, then follow Nick's instructions.

    Another useful website is http://www.800-airwolf.com/ and look under tech support. They have a whole section on 2 cycle maintenance.

    Bill.
      
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  • Re: TO MUCH FUELL ON THE PLUGS 618

    by » 13 years ago

    Yanis - One thing that I have not seen addressed yet on your 618 is the wear that you will have on the slides and idle stop screws. As you have noted you are not able to adjust the idle speed, this is because of the wear on the contact area of the slide and slide stop screw. You either replace the slides and stops or use what you have available to true up the end of the stop screw, as it will have flat spots, then increase the depth of the screw travel or the length of the screw. The slide and the slide cut-away are critical components in the proper fuel/air ratio that the carb controls. Wear on these components will be accelerated by the amount of idle time, quality of idle and the efficiency of the air filtering system. It is my experience that when you accumulate enough hours to wear these components that the simplest and cheapest way of repair is to source complete carb assemblies.
    Dennis
      
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