TOPIC:

1978 KZ650

Here is the problem. I was adjusting the rear brake light switch to come on earlier, and the main fuse (20A) blew. I checked the nearby wiring visually for any damage (I couldn't see anything) and replaced the fuse. I turned the ignition on and depressed the rear brake pedal a couple of times, and the same fuse blew again.

Any suggestions on where to locate this problem?

Sounds like a possible short inside the brake light switch to me. Wasn't shorting until you adjusted it, I would try and see if it comes apart and check it out.

+1 on checking the switch assembly. Also clean up the connections in your fuse box. My 77 kz650 was blowing main fuses left and right because of resistance that had built up at the fuse due to minor corrosion (didn't even look corroded, just dull). I polished up the clips and never had an issue again.

if the wires are run inside the bars, get them out, I had a lot of issues until I removed them and fixed all the bad spots.

Try resetting the switch to the position it was in before you changed it and see if it solves the problem.

That will either prove or disprove that the switch it the culprit.

If the problem persists then maybe time for a new switch / bebuild.

It may take a few tries, but you will figure it out eventually.

I replaced the rear brake light switch, installed a new main fuse, and everything seems to be working great.

Thanks for all of your suggestions!