Quote from hornschorsch on 09.10.23 at 20:26:08:Anja, ich glaub das Thema ist durch...
Technisch gibt es aber immer was neues, vorallem nach 3 jahre

I had the issues with a black plug aswell. The air inlet contained a real oilfilm, so without any doubt it was due to the breather.
I think all becomes worse when parking on the jiffy instead of the centerstand: when shutting down the engine the airflow stops, oil condensates and runs into the breatherpipe downhill into the inlet of cylinder 1. My trouble became worse since I removed the centerstand. But this is a good fix sofar:
I combined some of the aforementioned solutions: the frame connection of the xv750 and the upward facing hose of greg. The frame connection has some under pressure, which feels good to maintain. The upward facing hose makes oildrops run back into the cylinder head. So far it works like a charm. At the bottom-frame-connection-point I also connected a transparent hose with a plug. In some time I can report how much oil seeps doenwards. (So far none)