The picture above is representation of GY6 wiring diagram. The picture can be right clicked on and saved to your computer to view as a large picture file. This is just intended as a guide or example wiring diagram of a GY6 engine. This diagram was used because of the CDI that has two plug ins. Notice the black/white stripe wire into the CDI and that wire can be traced to the ignition switch and the handlebar kill switch. It is this wire that is disconnected for trouble-shooting any NO-SPARK engine. By disconnecting said wire, you will eliminate the switches and re-test for spark at spark plug. There is only three items that control engine spark and they are the ignitor or stator magneto, the CDI and the COIL. Again find the kill wire coming from CDI running to switches and disconnect switches from the kill circuit for easy testing of the ignition components listed above.
Numerous diagrams and trouble-shooting sections found in the Honda Clymers Manual sold here on the web-site.