**SOLVED**

1978 DT100e

I've read through all of the no-spark posts here a few times, and nothing has helped so far.

I'm checking all the wiring for continuity, and discovered that the yellow, the black, and the green with red stripe wires all have continuity. I'm wondering if this is a short. I'm admittedly not great at reading wiring diagrams, but I do have what I think is the correct manual, downloaded from this site.

I've replaced the coil twice (latest was top shelf), replaced the condenser, rebuilt the kill switch, checked the neutral switch (maybe not good enough), replaced the points, and a bunch of other stuff. I even rigged up an arduino as a voltmeter to see if there is output from the magneto and I get nothing (I'm a novice, so maybe that didn't work well enough).

I'm hoping you wise folks can help me out. I can provide pics if necessary. I'm still in the process of checking all the wiring, but this seemed suspect to me.

**Turns out I had the condenser wire connected to the wrong side of the insulator on the points, so it was shorted.**
*Edited for clarity
 

Pretty hard to believe you've read all the no spark posts because your "continuity" question and the fact that the "output" really means nothing even if you could measure it because there are no specs and it's a brief spike of voltage that creates the spark have been discussed many times.

99% of the time it's simply dirty point contacts. You need an ohmmeter with an Rx1 scale connected to the black (probably black/white) that goes to the points in the stator. Analog (swinging needle) meter is best in my opinion... but you've probably read that dozens of times now.

Point open you should have a reading of 1 to 2 ohms. Points closed you should have a solid connection to ground, same 0 resistance reading as touching probes together.

Not sure that you should get a reading from 'Black' [which is ignition source] to the others which are lighting/charging. But then again, very early DT's earthed source into the lighting coils so maybe in their case but not sure late models did that. So food for thought [hope i'm not confusing things]. Just realised i don't know what model but wildly guessing a DT250 as they went CDI in "79. I think i put a video up once of my swing needle multi meter showing the variation. I'll go find it.
Ok here's my meter. IGNORE the fact that it starts from '1' & imagine it's zero--can't get it to zero out but meter fault. SO--it shows a definite reading getting towards 2 ohms, bit less, but a deffo reading. So hope it helps.
Found also a short vid of how far i needed to turn the flywheel. Think i was only trying to show eyeballing the points gap. So in reality you wouldn't need to move it that far to get an open & closed reading on the meter & just a fraction forward & back over the opening moment would suffice. Bit of a hard to watch vid.
youtube.com/shorts/qVm-uhxIAT4
youtube.com/shorts/pf2lPN8x_YI

Which 1978 Yamaha Enduro do you have?

& welcome also.

Thank you for the response, and videos! I believe the bike is a dt100e based off of the Vin. I'm going to get an analog ohm reader, and get back to work. 
Thanks again!

Sorry I failed to mention that. Based on the Vin I believe it's a dt100e. 

Thanks for the feedback folks. Turns out I had the condenser wire connected to the wrong side of the insulator on the points. Haha

Ahh, tricks eh!!, always something new, & the good thing is you sorted it yourself--maybe with a little help.

You all were great help. The analog ohm meter I got today helped me to see that there was absolutely a short, and I wouldn't have got that without all the comments.