Persistant Blow of 20A Main Fuse

Something caught my eye in your last postings....
Disconnect the headlight harness plug and re-test....
Fuse blowing?

78 KZ650 D1

I started a thread about this a while back but haven't been able to work on things for a while. I figured I'd start a new thread because so much has changed since the first post.

My main 20A fuse blows as soon as my bike warms up. I fire up the bike and without touching it at all, the fuse will eventually go after about 2 minutes. If I replace the fuse immediately after that and try to start the bike again, the fuse will blow instantly. Sometimes it blows as soon as I turn the ignition key but this is only after the bike has warmed up.

Due to scorch marks and excessive heat (will burn your fingertips) around the connections to the reg/rec, I thought maybe I had a bad reg/rec. A couple people told me to unplug the reg/rec and see if the fuse still goes. So I did that, the fuse still went.

This leads me to believe there is a grounding problem elsewhere, though, I have searched high and low on this thing without any luck. I've opened up the controls and headlamp almost a dozen times, no exaggeration, and can't see anything.

Is there anyway to use a meter to track down something like this? I feel like I'm just shooting in the dark here.

...It all started when I opened my headlamp to tighten the nut holding the left signal light to the headlamp housing. Now you're all thinking, "Well, your problem must be in there!" Maybe it is. But like I say, I've had then thing open so many darn times and can't see anything wrong....