I have used Amsoil 20W50 and am presently using Castrol Actevo 20W50. The bike only has 125K on it.

Thanks for the info. After perusing 'bum's site, it appears that my engine probably doesn't have the drain port in the breather cavity, based on its ...

Therein is my problem. At the right rear of the block is the vent valve(called non-return valve on the fiche). I have a new hose that goes from the ...