Ok, first off, that was a lot of video for ... a failure to start issue?
1) if your v/r goes bad, chuck the battery, but...
2) replace the V/R FIRST. Why? because if you put a good battery behind a bad V/R, sometimes the battery gets cooked.
3) if you get kooky readings off the multi-meter, get another gauge / meter to compare with. It’s easy for a multi-meter to get fried via a mistake.
The video ends with your bike starting, but possibly not holding a charge? What is running on the bike’s electrical system that could drain a healthy battery?
:dontknow:
probably nothing. However, a battery that’s been cooked by excessive voltage? different story.
At first, you were seeing, if I recall correctly 19 v at rest, drop to 12 when you tried unsuccessfully to start? That’s a big drop, even if the numbers are kooky.
You should back this up with another gauge / meter. I’m betting at rest voltage is closer to the 13-14v range, but I’m betting the drop while starting is going below 12v, and I’m betting well below. You charge it up and the battery temporarily has enough juice but it won’t hold that charge, possibly even on a trickle charger.