Ok, so when flipping, we do get a pulse from the hall sensor, but what is the offset between the rising edge of the sensor and the desired time for the ignition? If there is no offset, and you use a capacitive system, starting the engine should be easy (from a CDI point of view). If there is an offset, or if you're using an inductive system, it's a bit more difficult. The problem with inductive systems is that you can't run a continuous current through the coil, waiting for the edge from the sensor to generate the spark. If you just keep the transistor on, and thus have a continuous current through the coil, it could overheat and fail.