1100ds head attachment question

[SpikeC]

 I have a question for the techs out there. I have the horizontal head off of my 1100ds engine, and the manual that I have shows an o ring under the washer that is under the head nut. There was none there when I removed the head. Is this a change in the production or did they do this special for Bimota?

[ducpainter]

They don't show an o-ring in the parts fiche for the 1100, and I doubt Bimota pulled all the nuts and washers to install o-rings.

What manual shows them?

[Düb Lüv]

Here's from a 1000ds if this helps

[SpikeC]

 Thanks, but that is a different engine. My manual shows the same images, but this motor never had the o rings in those positions. 
I can not for the life of me imagine what the purpose is of placing an o ring in that position.