Hey, I have something unusual happening on my vespa grande. The rear bulb is a two filament bulb and it has two contacts on the lightsocket and bulb, but only one filament functions. when the taillight is on, the top filament glows a little bit and when you hit the brakes, the top filament gets brigher and the bottom one does nothing, also the bike quits if it's idling. and then when that filament burns out, the engine kills when you hit the brakes at any speed. I'm gonna look at it tomorrow, but if you know what it might be, it'll save me some time and I would appreciate it.