New guy with carb question

[flying dave]

Hello all.  First post.

Bought a 07 500F for my stepson to learn to ride on.  Bought it from someone off of another bike forum that I frequent and made the mistake of never riding it so I am not sure how well it ran before.  Anywhoo, stepson put maybe 200 miles on it and lost interest. It sat for about a year and now that he is in college it is time for it to go.

Chasing some running issues at the moment.  Sometimes it runs on two, sometimes on one. Hanging idle also. First mistake was I had the carbs cleaned by someone else and it actually changed sides somehow, with the right side now cutting out.  Also seems to only run on one petcock setting which I believe is prime.  One thing I have read here is that the carbs changed around 04. So, I am doing what I should have done in the first place and am digging into it myself.  First thing I have noticed is that my carbs do not have the small vacuum o-rings in the top.  Microfiche doesn't show them either.    Researching here some threads say the newer carbs have it and some don't. 

What is the real answer?  If they are not supposed to be there then that is one less thing I need to worry about.  If so, I found the o-ring part number on the older carb fiche and will get a set.
What say you?

[jdoorn14]

Your carbs will not have the small o-rings. 2004+ carbs changed this.

[flying dave]

Thanks.  The recess is there if I recall but I wanted to make sure before I moved on to other areas.