94 GS500 bogs at idle, won't rev

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My 94 GS500 started to get boggy at idle and occasionally wouldn't rev but just putt at a sub-idle speed and then die.  If I could compression start it on a hill, it would clear and run OK.  This usually happened before the motor was fully warmed.  Then it started doing it when warmed up if I let the the throttle fall to an idle.  I'd have to keep blipping the throttle while at a stop light.  Now it won't start, will start to catch, chug a few revolutions and die.  Fuel delivery is good, floats are set correctly, carbs are at stock settings.  If I put in a fresh set of plugs, it fires up but then sputters and dies.  The spark is not a fat blue crackling flame, sort of yellow, but it's there.  Could this be electrical?  Corrosion buildup on a spade connector?

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Checked the spark today and it was barely there.  I think it's electrical, but where to start is the question.  Both cylinders have the same problem, so it probably isn't a bad coil.