Modern Vespa

I know this has been discussed ad nauseum... I'm blowing bulbs on my 65 - 6 volt bike. Started with the Festoon bulbs, and now it's blowing the pilot bulb too. I made sure I have a good ground at the tail light. There is a ground wire that connects to the housing and it's solid. Good continuity. No problems there. I measured the voltage output at the Festoon bulb and measured 7 volts at about 2/3 throttle.

My question then. Is this indicative of a coil on the stator going bad? Should I replace that one coil, or just go to 12 volt bulbs as other people suggest?

greg change the coil. its like 25 bucks and takes about an hour to do. i did my blue/yellow lighting coil recently and it was super easy.