Hi, I decided to swap out my old FD750D-BS03 with a new FD750D-S03 on my mower since it was not charging and the motor was 22 year old. The old motor was running fine but it kept draining the battery since the regulator was not charging the battery. I removed the old and installed the new motor, now the new motor is not firing up. I checked the spark and the unit would spark when I removed the kill wire on the coil. However, with the kill wires removed from both coils, the engine still does not run. I checked all the connections and everything is hooked up like it should. Any ideas? Thanks in advance.