Thanks for all the replies!
When I first worked on the bike the oil level was VERY low and very black. It was supposed to be within it's change schedule. The magnet on the drain bolt had a good bit of fuzz on it, no chunks no hunks, just fine sludgey goo of magnetic particles. None of this was very good, in my opinion, but I didn't know what to make of it yet. I didn't have a detailed maintenance record or anything like that.
Ordered a complete gasket set and opened up the right side cover because there were bits of gasket coming out and oil leaking over the swingarm, chain, inside the rear fender, all over back wheel. this is characteristic of oil coming out the airbox but I didn't check it then. The gasket bits were no big deal, just extraneous bits around the drive sprocket cover if you know what I mean....
So I did overfill at first, it was hard to gauge, and info online stated anywhere from just under 2L to 2.3L...
A few days later I checked the oil while hot on the centerstand, and it wasn't showing up in the window. So I added a bit more and the next day it pushed it out the breather again and the level was back juuuust under the window. I left it as is, and there was very little oil coming out, but after a week I checked the bike (it's my friend's bike that I'm trying to maintain for him) and the oil level was too low for my comfort and looking pretty black, so I added some more and it spit it out.
I have since learned about the oil/air labyrinth and the gasket in the breather chamber, and I'm very eager to get it opened up to see what's going on in there.
I will check for the oil pump o-ring when I'm in there as well. I have some oil change kits on order and I'll sort it out when they come in.
The air filter looked fine, but I will check it again. It has a plastic cover over it that the dealer added at some point after purchase, it seems that it's trying to direct air from the little vent in the back of the airbox directly to the filter, but it also keeps the oil off.
I suppose a compression test is in the cards.