That looks like the the cover for yer vacuum, for balancing yer carbs. Needs to be there or will draw air in and bike will run like sh t.
Yeah that's what I thought too! In fact, when I was carb sync'ing, that's where I connected the hose. I learned it's not that one. The vacuum port is just a little bit further up on the VStar 1100 and points straight out.
I went to the dealer and they told me it's another vacuum port. Not sure why there's 2 so close together.