I have looked at some exploded diagrams but can't seem to discern what would go in the vacant hole in the pic attached: it runs inside towards the sump drain bolt and seems to be threaded for about 4cm. It does not seem to be a crankcase bolt. Any suggestions? Thanks, Ramon
Should I then blank this hole off? What is it's purpose?
If there is a cheese head screw down in the bottom of the 'ole, does oil run out if you remove it?
You need a cheese head screw and that will tighten the bottom edge of the right hand crankcase to the bottom edge of the left hand crankcase. The threaded portion is in the left hand crankcase. Most likely a whitworth screw. If you leave the screw out you will most likely have an oil leak from that area.
.. to forget about that one when you split the crankcases (literally in some cases!)
Great - now that makes sense - I will see if I can shine a light down its full depth and see a cheese-head head looking back at me. Certainly there is no oil leaking from there (though from every where else around the engine!).