This 5-pin 1-plug type W rectifier (also sometimes known as a "voltage regulator") is an excellent little piece of motorsports electronics that may just be the missing piece needed for your project.
The purpose of a gas scooter rectifier is to prevent the capacitor from discharging prior to ignition (turning the key). Upon ignition, the rectifier stops charging the capacitor, allowing the capacitor to transfer the 400-600 Volt charge to the ignition coil.
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Proposition 65 Warning