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Interesting spark condition...

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  • Interesting spark condition...

    My latest project is a 500 Virago, V-twin, two coils, two carbs.

    The rear cylinder has great spark, but the front has none...until about three seconds after I stop cranking the starter. I only discovered this when I reached to adjust the demo plug and got a jolt (who looks at the spark plug after the starter is off?). This also explains some 12-gauge backfires I've gotten after trying to start it, I assume because the spark lights up the mixture through an open exhaust valve.

    I vaguely recall this being mentioned on XSes in the dim and murky past, but can't remember. Anyone have an idea about where my quest begins? Coils, TCI, timing, bad karma?
    "Time is the greatest teacher; unfortunately, it kills all of its students."

  • #2
    Probably TCI...just guessing because of the way coils work...

    Coils are energized, and build the field, but they don't spark till the ground is interuppted and the field collapses.

    Sounds like your ignition is not breaking the ground for that coil....until you turn off the key and break the positive.

    Check pickups...maybe the bike has two sets...and the one for that coil ain't working...
    CUAgain,
    Daniel Meyer
    Author. Adventurer. Electrician.
    Find out why...It's About the Ride.

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    • #3
      Very close, Daniel.

      The TCI will shut down after a minute if the engine fails to run. What you're seeing is the TCI shutting down, cutting off the coil simulating a cylinder firing.

      Check the pickups, then re-solder the TCI pins inside the cover. Wait. IIRC, the Virago TCI is a sealed unit

      Check out this link to a site where they explain how to cut open the TCI for the re-solder. Not easy, but not as scary as brain surgery.

      TCI repair

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