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Pinned Multimeter Coil Test – Twin lead coils

Discussion in 'Yamaha 250cc In-Line 4's' started by GreyImport, May 28, 2017.

  1. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Multimeter Coil Test – Twin lead coils



    Primary : multimeter on 200 (ohm side)

    probes on + and - terminals of coil

    primary should read around 2.8 ohms


    coil test 1.jpeg


    Secondary : multimeter on 20K (ohm side)

    The secondary windings are isolated from the primaries. These are double-ended coils, so measure the resistance through both spark wires (without the caps).

    secondary should be around 15K ohms


    coil test 2.jpeg
     
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    GreyImport, May 28, 2017
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  2. Brandon Otte

    Brandon Otte Well-Known Member

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    @GreyImport hi again - it’s been a while, thanks for the information on testing coils. Do you know a lot about cdi units? I have a 1995 XJR400R which will rev free not under load but break up badly around 8k rpm under load. Figuring out if it’s poor cdi? Thanks
     
    Brandon Otte, Mar 26, 2023
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  3. driftwood

    driftwood Well-Known Member

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    More importantly, most likely failures are ends of copper wire into caps screw and the 10kOhm resistor within the cap - the majority of mine on 3 bikes were corroded to worthlessness (retaining screw doubles as the plug connector, revealing lump of oxide). Coils and CDI are out of weather, away from the heat.
    So go cap-cap for 33kOhm.
     
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    driftwood, Apr 8, 2023
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  4. Brandon Otte

    Brandon Otte Well-Known Member

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    The coils and leads I have don’t have resistors in the caps at all - they’re just straight connectors.

    68D54573-A217-4AA5-A819-373EA7490E37.jpeg
     
    Brandon Otte, Apr 8, 2023
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  5. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    For an FZR250, leads without resistor caps are incorrect. Someone has bodged it. They will either need 5k ohm or 10k ohm resistor caps.
     
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    Linkin, Apr 8, 2023
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  6. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    GreyImport, Apr 8, 2023
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  7. Brandon Otte

    Brandon Otte Well-Known Member

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    Thanks for the quick response.
    So I have 5k ohm resistor caps which all read within 10%. I’ll put those on and see what happens. Is the resistor to allow build up of charge or something?
     
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    Brandon Otte, Apr 8, 2023
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