It works of course,but contrary to the battery situation you refer to in which there is no voltage to ground on the battery output,because the SOURCE (battery) has no ground return,here the source,the CDI generator coil in the engine is internally grounded.So there are allways high ac voltages on the blue and also on the black wire (when the kill switch is opened ),but that only lasts for a couple of seconds (until the engine dies),so it should be pretty safe.At least much safer than messing around with the blue wire,which ought to be left alone, IMO.