unidentified oil leak

[WeeStromer]

That's certainly worth looking at. I'm stripping my beauty to service it, valves, filters etc so I'll look over the bolts. Will report back once done.

[martind]

If the oil is on the upper level you have over filed it.

Eh? That’s where I fill up to what’s the correct way then?

[Rusty Nuts]

I'm with martind. Flat level ground, bike vertical, not on any stand, oil to upper level mark. That's full, not over full.

[STORMY]

Upper mark, level ground equates to 3.1 litres with a filter change, just an oil change 2.7 litres according to the handbook = just on the high mark.
Never had any problems (1000).
The only slight problem I experienced was a slight weep from the oil pour hole, just needed a clean and that solved it.
The lack of sealant causing OP leak does sound a bit troubling however