I was riding today in a pretty hard gear, and i heard some rough clicking. The top guide pulley was way to close to the cogs, and rubbing against the teeth. I looked up some info online, including BF. I tried to adjust the b screw to pull the guide pulley away from the cogs, but it had no effect, no matter what extreme i adjusted the screw to. I've never had to adjust this before, and in doing so i noticed that the small disc that the b screw is on, moves freely. By which i mean it rotates freely about 10 degrees in both directions. I imagine if this was in a locked position it would have the proper effect when i adjust it. But like i said, i've never maintained the rear derailleur before. Any tips on an fixing this problem? if necessary, i can supply photos, or even video. Thanks.
I never learned to ride a bike. It is my deepest shame.
Shimano derailleus are generally not designed to be repaired. In my experience, however, it may be possible to remove a c-clip and pull the pivot apart to attempt a repair, if you are sure that is where the malfunction lies... and you must be sure because taking apart anything from Shimano is accepting the risk that you might never get it back together.
If the bike is new the derailleur might still be under warranty, but if you take it apart yourself there is little chance for that. Also, replacing this derailleur might cost between $25 - $35 so it is not the end of the world if you have to get a new one.
I got ballsy and removed the derailleur and disassembled the pivot. What had happened was the spring inside the pivot had popped out of the hole it is meant to sit in, and naturally it unwound. So with much pain and frustration i managed to sit the spring and give it half twist before replacing the c clip. I took it for a spin and it's working like new. Thanks for the reply Lar, it gave me just the right amount of false confidence to fix it.