Regrettable Engine strip down !!!! I think " Follow up". But it's not over.

I really needed to clarify this point for myself and fortunately, my engine is sitting in the frame sans cylinder block and head, so........ take a couple of pictures. The studs between cylinders 1 & 2 and between 5 & 6 are mounted in the engine casing and you can see that the engine casing around these 4 studs have been machined to accept the o-rings mentioned. 

Now I'm wondering if I have confused these 4 o-rings with what I thought was in the head gasket??

 
Pic of the 2 studs between #5 & #6


 
Pic of the 2 studs between cylinders #1 & #2

 
Note o-ring #16 (12mm o-ring)

The O-rings mentioned by Kawboy are located between the engine block and the cylinders. If they were to fail, the oil would not enter the cylinders but would leak out of the engine.



In cylinder head gaskets of all brands, the oil passages are sealed with copper washers, not rubber ones.



Have you taken a look inside your airbox?