[Closed] xtr pistons too far retracted - help...

I was in the process of sticking some new pads in my 980 brakes, and I think I've pushed the pistons back too far.
When the lever is relaxed they sit flush with the caliper body, and when the lever is pulled they protrude by just a couple of mm.
In this situation the brakes work but only right at the very end of the lever stroke.... 🙁

How can I get the 'self adjustment' to work so the pistons don't fully retract back into the caliper when I release the lever?

(Brakes were in air free condition before the pad change & bleeding since has not shown any bubbles)