recently my Vespa had some ignition stops, ran again, ignition stop and finally the engine went off, on the middle of nowhere on a small road. I checked my toolbox under the seat of my Vespa V50 and the only tool I could find was the spark removing tool. OK, I went for it and screwed the hot thing out. And bingo! A piece of dirt or coal was between the electrodes so no wonder why the scooter did not work any more:
Cleaned the spark and bolt it back, voilà! Engine running again. Guess the piece of dirt came from either the cylinderhead or it was some dirt that went through the fuek hose all the way through carb etc.
In any case, I wanted to let you know what happend and the solution, so if you have the same go for the spark first thing!