Here are some pictures:
Around the cam chain tunnel some wear can be seen:
And cylinder base:
And also some wear on the cylinder:
So now the question is how much to do about it?
New gasket and some liquid gasket? Bolt it back up give it some road miles and see if it holds up and then call it a season, winter is around the corner.
Then rip the front off and do the same (would guess its not far away from leaking). And then add a thick bead of silicone around the bases to keep stuff out.
Exhaust valve are showing some deposit buildup:
But is it worth putting to much time and money into this engine? Sealing the bases as best possible and drive the shit out of it until something blows? And then see if its time to get hold of a used engine or maybe an entire new bike, but that would be a decision for later.