GY6 50/150 CDI for 139QMB/157QMJ Scooter Engines

Stock CDIs are the same for 50s and 150 engines and look the same. The CDI tells coil when to fire.

If you think your CDI is no good you will not be getting a pulse to coil to fire spark plug. If you have voltage in other areas and no spark your CDI very well might be no good. These do go out as well as coil and magnetos these are main parts that create spark to run scooter.