It is too my shame that I have to admit I’m really struggling to set up my brand new xt 8000 rear mech. Problem is that the top jockey appears to rub on the cassete in the 42 cog. I thought the B screw adjustment would fix it but to no avail.

I’m running 1×11, think my mech s the shorter of the 2 varieties but didn’t think that would be an issue…

please help.i’m meant to be riding at 2pm and the lbs is shut!

Does it work ok besides? Can you live without 1 gear for now?

P.S.
I’ve replaced 2 mechs in one session – first took 5 mins, the other a good hour and I ended up having to go to the LBS to get them to do it (for shame!). Generally if it’s not working out go back to the beginning – re-set everything and start afresh instead of winding yourself up trying to tweak what’s already out.

Even with the b screw all the way in?

Chain length?

aaaah…just realised the b screw was in fact the h limit screw…sure its on a different place then the old version!!!

oops

will try again

sorted…an hour of my life I’ll never get back. Literally a 2 min job once i’d stopped being a fool

Can you live without 1 gear for now?

the answer to that has to be yes but possibly not the gear nominated by the OP 8)

Easy enough to go back to the beginning once you know what’s what.

Shift to smallest cog on the rear shifter. (and the middle ring if running a tripple. On the Front)
Unscrew cable bolt slightly so the cable is slack to take the cable out of the equation.
Set H, L and B screws by manually moving the derailleur.
Adjust cable tensioner screw on the shifter to allow a good 2 full turns in either direction.. I. E. 2 or 3 full turns from fully screwed in.
Set cable tension (your shifter still thinks it’s on the smallest cog on the cassette).. You don’t want any tension or any slack on the cable, so just pull it through and bolt it back up with no sag, but no tension either.
Put chain back on.

Then shift up and down the cassette repeatedly, noting any skipping or jumping whole cogs, and tune the skipping out with the barrel adjuster..

You need to do this with the bike upside down on the floor, or ideally the right way up on bike stand.