Jockey Pulley Rubbing on Largest Gear

[Kloosty]

I'm currently adjusting the rear deraileur on my Specialized Sequoia and I've noticed that even if I screw the B-tension all the way in, there is still some rubbing on the largest gear. Is there anything I can do to fix this?

[cyclerUK]

What size is the largest rear sprocket?
Have you changed anything lately?
is the chain the right length?

If you run out of adjustment then it's possible to put a longer screw in, or remove and fit the existing screw in from inside. You shouldn't really run out of adjustment if everything is normal.

[Kloosty]

I don't know about my sprocket, where would I find that information?
Yes the chain just got replaced.
The mechanic at the bike shop put the new chain on so I would have thought it was the right length but now I'm having my doubts.

[cyclerUK]

To count sprocket teeth.
Put a mark on one of the points and then just count round. Some sprockets have the size imprinted on them. Too big a sprocket could cause jockey wheel rub.

But as you have had a new chain fitted and it was O.K. before then that would be my favorite culprit?

To check the chain length:-
http://bikeride.com/calculate-chain-length/

Obviously hard to do when the chain is already fitted.
But put the chain on large front chainring and largest sprocket at the back. There should be a slight amount of slack. (not sloppy and not tight.)

[kcairo]

I have the same problem; the pulley is rubbing in my bottom two gears. The b-tension screw is literally not doing anything at all. I have an old dura ace RD-7400 6 speed derailleur, and if you look at the way the b-tension screw is set up, it's pretty obvious it won't do anything. I'm thinking about overhauling it (a la http://www.parktool.com/repair/readhowto.asp?id=76 ), but I'd definitely rather not.

Is there anything I could do to help figure this out like take some pictures, remove the derailleur and take pictures, maybe video, anything?

Also, I just replaced the chain (the length is correct, I'm sure of it), so I don't think that it's the problem, though maybe putting a chain.

Thanks a ton!