CDI issues that doesn't match any diagrams online.

Hi guy's
Newbie to the scooter world and I don't own one personally. My granddaughter has just got herself a cobra 125 scooter with the what seems the usual GY6 engine. (BN152QMI) It was purchased as a non runner being told no spark. It's a project she wants to do for when she's 17 next year, she wants to learn how to fix her own bike if the need should arise.
I had a look on youtube on tracing electrical spark issues and went into her garage armed with my meter, when I got to the CDI unit I was expecting to find a black and red wire on the 2 wire plug part but it only had a black wire and 3 wires on the four plug part, then on the ignition coil to the spark plug again I was expecting to see 2 wires but this had again just a single wire, I tracked down said ignition coil on fleabay but it listed motorbikes and scramblers as to what it would fit. I'm waiting for a new tool to arrive so I can remove the stator cover so as yet I have no idea how many coils it has. Rather than mess about I decided as these parts often kick up issues I'd purchase all new ones for the bike. Can anyone throw any light on as to why the CDI has only the black wire connected? Many thanks guy's