This magneto rotor needs to be removed with a special tool. It is a 16 mm screw. If you don’t have one, you can find a suitable screw yourself. It is best to use a magneto clamp to fix the rotor. , and then just tighten the screw. You can also tap the screw while tightening it, so that it can be removed more easily.
In the picture, it seems that a hexagon socket screw has been removed. It is used to fix the overrunning clutch behind the magneto rotor. It is not necessary to remove it to remove the rotor.