Lost Spark while riding '78 XS650

From the video it sounded like you hit the kill switch (which you didn't). Did I hear that correctly?
Most electrical components will have to cool off to function again. So I'd guess coils & condenser are ok, because your bike started right up again in the driveway didn't it?
I'd suggest taking your tank off, unplug the coils, plug your VOM into the harness side of the 2 wire coil brown. Ground the VOM negative. lead, turn the ignition on and start wiggling wires from the battery into the headlight shell, to the handlebar switch. When the VOM drops...bingo.
My 2 cents. Good luck

I might have wiggled it to see if it would come back.
Your suggestion about wiggling looking for voltage changes is a good one. Keeping this in mind for future use. Don't forget even though I believe i found it, these postings are used by others having similar situations so good suggestion!
 
NO WAY this left Yamaha looking like this.
Someone hacked at this at some point.
Previous owner was original owner but did not work on the bike.

IMG_2347.jpg
 
Good troubleshooting. If there is 1v drop at the ignition coils, it is worth taking apart and cleaning the contacts in the kill switch and the ignition switch. I had about 0.8v drop which after cleaning reduced to 0.4 to 0.3v drop. Well worth doing and surprisingly easy just following the guidance here.

(To get the best possible spark at the plugs, installed a relay switched by the red/white wire. It sends battery voltage direct to the ignition system).
 
30 mile ride today and tried to keep it at 4K-4.5K rpm to work the ignition more. That's about where it was failing last time. All good so far. I also put in a new Yuasa AGM battery on Thursday. Breakfast bike meet tomorrow and apprehensive to bring it till I have more time on it so will bring the 83 XJ650.
 
NO WAY this left Yamaha looking like this.
Someone hacked at this at some point.
Previous owner was original owner but did not work on the bike.

View attachment 339586

Perhaps can help someone .Not saying it is right ..but putting it here
feel free to disregard
Those connectors can have multiple issues after 50 years
And many DIY can have been there
Corrosion and the pins can move if the barb is not in place

The connectors are expensive buying new .and needs special pliers and caution is still needed
So I have gradually started to solder and use shrink wrap mainly in ignition Circuit
Mostly no connector at all .Sure one needs to cut it open if changes but is easy

A month ago I rewired .. Under those metal in the picture after using the correct pliers .I held a big soldering iron under
and soldered it also
And then Shrink wrap

I am not saying if it is right or wrong but fex for Fault finding in ignition circuit this a 100 % certain method to get correct Voltage at the right spots

Over the years it has rarely been the wire itself that has caused the problem 3-5 % of the cases
Fuse Holder Ignition switch kill switch and these connectors.
 
I did do my best to fix the crimp and crimp down onto insulation and then I soldered the end. I don’t like the solder flowing into the insulation too much cause that can make the cable brittle in the transition
 
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