You can do manual tracing of the wire from the cdi. If it goes to the regulator then it is d/c, if the wire goes to the stator, then its a/c.
Here is a simplified checklist to determine the type:
Headlights turn on with key, DC. Headlights turn on with engine,AC
Engine does not run without battery, DC. Engine runs without battery, AC
CDI box is pretty large, DC. CDI box is smaller, AC
There is one wire on the two part plug, DC. There is two wires on the two part plug, DC.