With the key switch plugged in to the main harness and the kill switch black/white plugged into black/white on the main harness  and the black from the kill switch plugged into the black triple on the main harness in the headlight  bucket , now i dont have the key switch mounted on the bike, but it is plugged in. so i flip the key switch over and touch the black probe to the black wire soldered to the back side of the key switch and the other probe to the black/white wire soldered to the back of the key switch,  no battery hooked up .
I did another test with ohms, with the kill switch in the run position and the key in the off position I get a reading of 0.00 . 
with the key in the on position and kill still in the on position , I get a reading of 1 . , i then switch the kill to off with the key still on position  and i get reading of 0.00. I switch the kill back to run and I get a reading of 1. I shut the key off and get a reading of 0.00 .
does this sound correct to you? I think it does. Please let me know if I'm wrong
Thank you!
John

John, I will have to read what you wrote carefully...  I'm pressed for time right now but at first glance it does sound correct!

Took me longer to figure out pictures than expected...  you're already way ahead of me!  Next test would be to use one meter probe on the black/white at the harness side of the key connector (see photo) and the other probe at the harness connector the little wire on the ignition coil plugs into.  What ohm reading do you get? 

Your plug has 2 b/w wires my plug only has 1

The 75 harness must be slightly different than my beautiful new 74  DEET harness . I made sure all the wires are plugged in good , I put enuf gas in the carb bowl without putting the gas tank back on and started it , the key and the kill still didnt shut it off  . I turn the key on and The turn signals work the taillights work the tail light switch on the handlebar control works the horn works, the key shuts them off,  it just don't shut the bike off , while it was running i tried unhooking the black wire from kill switch and touching it to bare metal handlebar , and not touching it to bare metal , didnt work either . I think It's got something to do with the black/white & Black wires somewhere maybe because the kill switch has 2 wires when the original only had one wire, is there an emoji with a guy pulling hair out of his head? 
 

Another thing I was wondering is my battery positive doesn't have the fuse link directly plugged at the battery positive, rather its plugged into 2 other red wires, but we went over that already , I did notice however on a Google image, under the seat of a nice original dt250a that the red wire at the battery had the fuse link hooked direct at the battery and the way mine is hooked up is to the 2 red females on the main harness near the battery

Take a breath.  The harness might be constructed differently.  The two black/whites connect in the plug on this one, yours might splice inside the harness. (Many Yamaha harnesses have splices hidden under the outer wrap)  This is not a problem. 

The question is the same.  Do you have continuity from the black/white wire at the key switch connector to the harness connector the little wire the ignition coil plugs into? 

OK. With the kill on the off position, black probe to black in the main harness side key switch connector other probe to black female on main harness ( should I do this when it plugged into little wire on coil?) I get a reading of 0.00
If I take the probe and touch b/w in the harness side of key connector other probe in black female on harness I get a reading of 0.01
With kill switch on touching black probe to black in the harness side key connector other probe in black female on harness I get a reading of 0.00
If I probe b/w in harness side other probe in black female reading is 1 . Pretty sure I got that right yes.

I got a big calus on my right thumb from typing

I just did another test doing like you said in the last test except this time I went further back to the black wire that connects to batt negative. Probe Black in harness side of key switch connector, other probe in batt neg connector switch off 0.00 switch on 1.

This is all being done on black & b/white wires on the kill switch ...
I have the key switch unplugged when I'm doing these tests.