i would not say neglected, as the oil was always changed, air filter was clean as can be, and valves were in spec, tires and brakes are perfect, plastic looks brand new, swingarm doesnt have a scratch on it, forks dont leak. the issue was, not all bols were checked to be tight, hence why part of the carb fell off. no idea what was up with the auto decomp, starts so easy now. going to get the right plug before I do anything else. Then adjust the fuel air and idle. that was a true cold start in the video too, sound is bad do to my cell phone lol.
I'm thinking steering, swingarm, and linkage bearings. I've seen plenty of bike with fresh oil, but wasted bearings.
Something made that plug black. It could be something simple like running really rich which makes for a black sooty plug. If it was more of a wet black then it's is usually oil from either guides or rings.