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  1. #1
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    Using a Multimeter to check spark

    I was reading Eric Gorr's jetting info, and in the mechanical problem area he says to check if your getting a good spark with a multimeter. I do have a digital multimeter but what and where should i place the testers (wires) and what setting should i have the multimeter set at, theres a bunch of settings.

    this is what i have.
    http://en.wikipedia.org/wiki/Image:Multimeter.jpg





    Thanks!




  2. #2
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    A multimeter won't test for good spark. I strongly recommend against having the multimeter even touch the spark plug wire!

    The easist way to check for spark is to remove the sparkplug, attach the spark plug wire, hold the threads of the plug up against the motor case and kick the bike over. You should clearly see a nice strong spark jump the plug.

    If you are not getting spark, the multimeter can be used to establish why not by measuring the coil resistance and comparing to the manufactureres specification.




  3. #3
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    i think if you hook up multi meter to plug and kick it it would blow the internal fuse or fry the meter spark voltage is way higher than what meter is rated for




  4. #4
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    okay...io just re-read the info:

    Weak sparkÑWhen the ignition coils deteriorate, the engine performance will become erratic. Normally, the engine will develop a high-rpm misfire problem. Check the condition of the coils with a multimeter.




  5. #5
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    Your profile says you have a YZ250, CBRF4i, and Kaw 1125.

    Which bike are we talking about?

    If you have a known good coil then it is easy to make a comparison measurement on your suspect coil. Without a known good coil to compare against you will need to know what the expected resistance is. There is also a problem that an inexpensive multi-meter (if you paid less than $200 it is an inexpensive model) their accuracy on very low ohms is rather poor. Not a problem if you can measure a good one then the suspect one, but can be a problem trying to compare suspect to the written specifications.

    If you have the technical specifcations or a shop manual for your bike it should give you the expected ohms. Two of them, in fact: primary and secondary. The primary will typically be a very low number and measured across the two main contacts of the coil. The secondary will be a much higher number and is measured from the spark plug wire to one of the main contacts.




  6. #6
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    talking about the yz250. not sure if its a weak spark or not. I haven't looked, but i don't rember it being extremely bright. i'll check it tommorw. and i don't have a known good one, they're expensive.




  7. #7
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    no there not to expensive
    go to electric supply house
    get fluke model or greenlee or ideal
    good one there run you about 100$ or less
    just get digital one




  8. #8
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    no i meant a good coil...but i did find in my manul about what rmc_olderthandirt said, should i test the wires while the bike is running or should i just kick the bike over while the wires are in palce?




  9. #9
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    Quote Originally Posted by rmc_olderthandirt
    There is also a problem that an inexpensive multi-meter (if you paid less than $200 it is an inexpensive model) their accuracy on very low ohms is rather poor.
    its not the price its the make
    greenlee, fluke,amprobe and ideal all make good inexpensive meters as well as some high priced stuff
    use them alot at work




  10. #10
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    Quote Originally Posted by Badgadjit1
    . . . should i test the wires while the bike is running or should i just kick the bike over while the wires are in palce?
    neither. you disconnect the coil and test the resistance measured against a known value for a good coil



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