With yellow to ground open and white to ground open, it's a good bet that the stator has failed. The stator is just one continuous winding that goes around multiple posts. The direction of winding changes as you go from one post to the next. As you say, if you lose the single winding that powers the CDI, you will be walking.
Based on your comment it looks like DC power is used for the tail light. And yes you will get continuity between white and yellow. Think of it like a transformer. The yellow is just tapped off at a different point in the winding. That is what the wiring diagram is indicating. They show it at about 50% just for sake of clarity on the diagram.
Note that the stator windings could still be OK if you have a broken solder joint where it hooks up. You could also lose the ground due to severe corrosion but that is not likely unless the stator screws/stator plate/motor mounting bolts/frame tabs are in really bad shape. Get yourself a flywheel puller and remove the flywheel. It's the only way to see what is happening with the stator..
__________________
2011 EC250E
|