Headlight is out - KZ750 spectre 1982

Anybody know where I can get a tutorial on how to learn Motorcycle Electrical.
I'd like to find a book that teaches me to read electrical diagramming and how to
diagnose and use a multimeter. I just had my mechanic come over and test different areas
for voltage and resistance, but he threw his hands up and said he didn't want to
redo a whole wiring harness. I suppose I am suppose to check for voltage as a current
but not sure why to check ohms.

If you really want to gain an understanding of motorcycle (automotive) electronics you may want to enroll in a class on the subject at a community college. You would end up with a sound understanding of the subject that would enable you to troubleshoot your (or other ) bike's electrical systems. If you took such a course (and there may be some that can be taken online) and used the Kawasaki Service Manual as a guide you should be able to test and correct any of the electrical components on your bike. Here's just a sample below. Ed

www.clovis.edu/ot/blairp/courses/AT100/index.html

Youtube videos are handy. There are plenty of them that show how to use a multimeter. Or do an internet search for "How to use a multimeter". Get a digital unit. I use a VC97 - it seems to be good one - the robotroom reviewed a number of meters.

As for your headlight, I would check the fuses & the headlight bulb. The Spectre probably has an H4 lamp. The fuse box may have one position labeled "Headlight" - my 81 650 does. If those things check out, the manual probably has a troubleshooting procedure for testing the various components of the headlight circuit.

If you don't have a manual, search ebbaayy for KZ750 Shaft manual. The Kawasaki service manual is preferable.

Several of the guys here can walk you through checking your headlight. You do have a meter right? So it will be pretty easy for some basic checks.
Doubt you need a new wiring harness.