Hi and thank you all and particularly, this time, Geoff,
Thank you for the pin size; I will think before cutting anything…
My vertical head, MkII, does not seem to have an oil seal, unless it is above the bearing.
What I have at the top bearing is a labyrinth seal, which I also have on the horizontal shaft; that is to say, three rings cut in the shaft where it close fits the cover plate.
I am reliably informed that this seal works very well for thicker oils which led me to mention about the thin hydraulic oil.
I have found the modern equivalent to the specified Shell CY2 which is, as I mentioned earlier, Shell Vitrea 100. It is thick and gloopy, if you will pardon the technical term
Before stripping your VH, I would try the proper oil. If it still leaks, then do the head and all you have lost is a bit of oil.
Andy