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"Jetting" a saw by spark plug color

Post in 'The Gear' started by lumberchukk, Feb 25, 2008.

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  1. lumberchukk

    lumberchukk New Member

    Jan 3, 2008
    Chest Springs, PA
    In 2 stroke dirt bike land I've always jetted my bikes by using a few new sparkplugs and running the bike at different throttles. 0 to 1/4 throttle for the pilot jet and wide open for the main. I then check the color on the spark plug for that nice tan color that tells me I'm in the right place. Obviously white would be too lean and black would be too rich. Does anybody use this technique on their saw? I do understand there are differences where as I would change jets in my bike carb while I would adjust the low speed and high speed screws on the saw carb.

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  2. computeruser

    computeruser Feeling the Heat

    Jan 16, 2007
    East Lansing, MI
    I've always had good luck tuning by ear and by feel in the cut, and generally find that when I verify my tuning with a tachometer I am 250-500rpm below max rated RPM. Pulling plugs for color has never been necessary, and with good synthetic premix the range of color is going to be much less distinct than with older dino oil.

    The only place, in my experience, where tuning by ear is tough is with the low-RPM older saws (my ear wants them to run faster!) or with some of the 15,000rpm+ screamers, and for these saws I skip my ear and tune only by the tachometer.
  3. sedanman

    sedanman New Member

    Oct 21, 2006
    Adjust the low side first, this may not be the final adjustment, you'll re-check after the high side is set.
    You are looking for a smooth idle with crisp acelleration. On the high side if your saw is NOT equipped
    with a rev-limiting ignition, you will richen it up until it starts to "four stroke" or misfire then lean it out just enough to make it run smooth. If you have a rev-limiter then you NEED a tach, no other method works. After the high side is set go back and re-test the low side for idle quality and acelleration.
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