Motorized-bicycle-magneto-replacement, update: improving magneto contacts | bikeberry tips and tricks we've received a lot of concerns regarding electrical issues with the 2-stroke bike engine kits. if you're having inconsistent spark .... Correct magnet to crankshaft alignment for the 80cc / 66cc 2-stroke chinese bicycle engine., make sure this fits by entering your model number.; the 4-stroke flywheel magneto rotor helps generate spark for the cdi on our flying horse 5g and most huasheng 142f 49cc 4-stroke bicycle engine kits. This is going to be as basic as i can make it, but i'm going to try and improve people's understanding of how the ignition system works. here we go. first of all, we have to understand what voltage and current is. voltage is the potential. it's how much attraction it has. it's the measure of how enthusiastic it wants to get somewhere.