I (think) ive set up all my gears correctly but the keeps on slipping of the lower jockey wheel. The jockey wheel will take about 2 full rotations, with the chain slowly slipping of, then jump of, then straight back on again.
Sorry am a bit of a noobie when it comes to bike problems!!

n.b. Mech and Rear Cassette both XT (had about 1 years intermittent use – no more than 2 rides a week!). New XT chain fitted last week when built up new bike.

Stiff link maybe?

Easy to check – just run the chain through your fingers and check that each link can move freely. No need to take your chain off.

In my experience (albeit limited but with new chains) is that stiff links tend to be a recurrent problem – it will be fine for a few rides but then seize again.

very strange, usually you can turn a jockey wheel into a ninja throwing star and it still works fine. Does the jockey wheel turn smoothly if you take the chain off?
Might be crap inside the bush/bearing stopping it turning?
Should just be abe to take it to pieces and clean it, if this is the case.

Not sure it this was the problem or not – but the cage looked slightly out of line – so i bent/pushed it a bit – seems ok now – good enough for me to ride a couple of times next week.
Think I might just book it in to LBS for them check it out!

MAke sure your front sprockets aren’t worn. It’s very unlikely that it’s the jockey wheel. I run them until they are nearly discs. THey do very little and are simple designs. The problem will be something else causing the chain to jump.