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Can a bad ignition coil cause rough running at certain throttle position?

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    Can a bad ignition coil cause rough running at certain throttle position?

    83 GS1100ED
    Went through the carbs - thoroughly - twice! New rubbers, new boots, etc.
    That cured the previous running issue (only ran with choke).

    Now it starts and idles fine everytime, sufficiant pull at closed throttle to 1/8 throttle, skipping stuttering jittery..
    Goes like a race bike at 3/4 to full throttle.
    Most noticable at 3,000 rpm to 6,000, but I'm going by the throttle position.

    Vacuum synched to the best of my ability but truthfully its hard to hold still. Vacuum values fluctuate a bit.

    I ask if it might be an Ignition coil issue because my New dyna coil for cyl #2 and #3 tests at 20 kOhms when it should be 31 kOhms to 33 kOhms. The other coil measures 31 kOhms.

    I'd like to avoid spending the $175 for a coil replacement if its still a carb issue.
    ​​​​​​​Thanks in advance.

    #2
    Yes, it can. I rebuilt my '83 GS1100E's carbs, and the bike ran great as long as it was cool outside, it behaved OK. It would stumble between 1500 and 3000 RPM in warmer weather, then run correctly up to redline. It had some no-name blue coils, and I had an original stock set on hand, which cured the problem. I also put in a relay to get more juice to the coils. Like you, I removed carbs and cleaned again. It became clear to me that it might be electrical the first time I rode on a chilly morning and as the day warmed up things got worse and worse. Maybe you could find a cheap used one to test the theory rather than pay so much?
    Last edited by oldGSfan; 10-25-2024, 01:20 AM.
    Tom

    '82 GS1100E Mr. Turbo
    '79 GS100E
    Other non Suzuki bikes

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      #3
      This is what I learned... If you think it's the carbs, check your ignition...

      And I've had plenty of "carb" issues only to find out that one of my pickups on my Dyna ignition was dropping out.

      You can only clean the carbs so well before you need to look elsewhere.

      I also did the relay add for direct battery power to my ignition system.

      Current:
      1993 ZX11 - 2nd build in progress
      1977 GS750 (710 is getting closer)
      1998 Kawasaki Voyager - selling
      1998 Chevy C2500
      1999 Rav4

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        #4
        I'd avoid being stiffed by Dyna by simply fitting Honda MP08 coils from a CBR1000, Gold Wing, etc.
        ---- Dave

        Only a dog knows why a motorcyclist sticks his head out of a car window

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          #5
          Sounds similar to the issue I'm having. Bike runs great but when it gets hot it gets a serious missfire. 1980 gs850g

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