Not sure how experienced you are from your description. If this is new for you - have you made sure you are allowing the tab on the RD to clear the stop on the hanger?
If you are not doing this then you will get exactly this situation. Don't ride with it BTW.
Yes I have chekced the tab is in the correct place, it's not the tab that is binding up but there is friction somewhere stopping it from moving freely.
http://www.campagnolo.com/repository/documenti/en/2012_COMPONENTS_SPARES-PART_A-03-12.pdf" onclick="window.open(this.href);return false;
The tech drawing does show a bolt within a bolt as you guessed.
Maybe the spring end has come out of its retaining hole and binds when you tighten the bolt.
Many thanks for the tech download. As you say it does show a bolt within a bolt which I thought. From the Chorus up to SR it shows this two-piece bolt within a bolt.
I think it will be best for me to put a T25 torx on the inward bolt and try to undo it whilst holding the outward bolt from moving, that should untighten it I think? Then I will untighten and remove the derailleur and reinstall without touching the inward bolt ?
I'd like to see how that "bolt within the bolt" is fastened together. If it's a threaded connection, you would think there would be a risk of it coming apart on removal. Press fit?
Interesting that no P/N shown either.
Sorry, can you explain P/N?
Below Chorus it's a conventional one-piece bolt.
Maybe the tech manual has something?
I would like to see the workshop manual if anybody has one.