Hey. I apologize for the late response. I dont get any notice of PMs. I’ll look into that.
I took two more photos for you. As you’re facing the motor on the right side, one wire from the top of armature and one wire from an auto type condenser are connected to small lug on coil. The other wire goes to right side spark plug.
As you’re facing the motor on the left side, one wire from large lug on coil to ignition switch. The other wire goes to left side spark plug. The bottom lug on ignition switch goes to negative terminal on battery. The other lug immediately behind ignition switch on coil/starter switch bracket serves as ground and goes to positive terminal on battery. (12v positive ground setup)
I can see the lug you mention on the underside back by gas tank. On my motor there is nothing connected to it.
Hope this helps.