Hah! Finally a great lead. Based on general research, I strongly believe this is my entire issue. Video link attached.
So i opened up my clutch cover today for the hell of it, and I learned a few things.
-zero wear on the clutch gear and crankshaft gear. They look stellar.
-my friction plates and steels from my recent replacement also look perfect.
-fingers on the clutch basket and the slots on the clutch hub look extremely minimally worn.
-and of course, the basket moves a ton about its gear. There was an audible rattling when you jiggle the basket, and I can clearly see the gears weren't moving at all.
So I did some research and it appears just about every bike has "dampers" of some kind actually inside the clutch basket unit, which is one piece, because its riveted together. Not sure what types are common, but I can see that some bikes have rubber dampers, similar to the type in the cush drive in the rear wheel, and others, like the ninja, have springs instead of rubber pieces.
According to this DIY article on replacing these "non serviceable" dampers in your clutch basket, the "clutch basket *should not* move independently from the clutch gear".
I couldn't find a lot more solid information regarding how the dampers are supposed to be when they're new, but I am assuming that, much like the cush drive, these dampers of all kinds are only effective when there is no literal play in the system. As promised, heres the video of me handling the pieces on the bike before removal, and after pulling the basket.
As you can see in my video, there is gross play in the basket, and when I pulled it off, you can see the springs loosely sliding back and forth in their groves. I can spin the springs around along their axis in the groves very easily, the springs have clearly been permanently compressed.
It's really annoying that bike manufacturers' solution to this problem is a $300 clutch basket because 6 little springs wore out. It sucks, the basket is in great shape, the gear looks perfect, its otherwise a perfectly good basket ready to take on thousands of more miles. And just about every bike manufacturer sells an entire clutch basket as a unit, that you cannot disassemble. I haven't done any research on the topic, but that article mentioned replacing the dampers (springs in this case) with parts from aftermarket makes, but the way they are installed, you couldn't remove or install them without permanently deforming the metal on the clutch gear...
I may try to defeat the rivets to get inside it and see if I can make myself my own serviceable basket, by doing kind of what that article described.
I see other threads online about these springs being loose, but it seems almost every case that the rider only notices noise, not any performance issues or lash. It looks like people shim these, but looking at the design of the 300 clutch and the other bikes, I don't think shimming is a good idea, since retaining the shims would be hard.
All in all, I am pretty sure this is my issue. So I ordered:
-new clutch basket assy
-new center hub (damaged it in removal, I'm stupid)
-new nut and washer for the clutch hub, I had to cut it off, that thing was SEIZED on there. only 10 bucks for both, so why not.
Can I get any confirmation that you guys think this is indeed my issue? Out of all the steel gears inside my motor anywhere, I have seen zero visible wear on the teeth on any of them. Cam chain gears, all the gears behind the clutch basket like the oil pump and others all look as good as new. So based on that assumption, I am assuming my actual transmission gears are likely in pretty good shape as well. They are straight cut gears, and have a designed in amount of gear mesh to allow for proper shifting, and when I was handling the clutch hub and the countershaft after I got the clutch off, it spins the transmission very very smoothly in neutral, very little noise, no hitching or anything adverse whatsoever, so I would say it's in great shape. The clutch basket was the only thing I found that was blatantly messed up, and I was expecting to find something blatantly messed up to match with my blatant ridiculous lash, so to me that fit the description. It also makes sense that things like springs would gradually weaken/get squashed over time with use, so that fit the bill as well.
I need some feedback here, back me up if you think this was the right item to replace. It was a lot of cash, so if it was the wrong thing, I would certainly want to return my items...
Everything else looked as perfect as I could expect a bike with some mileage on it could look without taking the motor out.
Thoughts? Sorry for the long write up, I had a lot to share. Hopefully this could help some poor sap in the future with the same issue that I've got.
Thanks in advance fellas.