With the 1980 SG it should be simple to find out why you lost power to the tail light. There's only 2 things between the battery and the tail light.
Use your VOM to check for battery +12 volts at the main 20 amp fuse, and then check at both sides of the ignition switch. That's all there is.
I hope your bike doesn't have those original fuse holders (glass fuses). They can cause lots of intermittant electrical problems. If you still have them..............replace asap.
Use your VOM to check for battery +12 volts at the main 20 amp fuse, and then check at both sides of the ignition switch. That's all there is.
I hope your bike doesn't have those original fuse holders (glass fuses). They can cause lots of intermittant electrical problems. If you still have them..............replace asap.