Yay, I'm there I think. The problem was a combination of lack of experience (I had never even changed brake pads before let alone stripped and rebuilt calipers) and a lack of perseverance. The pistons were pushed right back initially to minimise the amount of air gap behind them which is the right thing to do, but this ultimately was the source of the issue, due to my lack of experience. I had pumped fluid up in to the reservoir using a syringe, and pulled fluid back through using a vacuum pump, all without much luck. So today I started afresh. I realised that the pads had moved a bit towards the disc so I pushed them right back hopefully to expel any air and sure enough bubbles came up in to the reservoir. Then I used the vacuum pump again and pulled a few more bubbles out. Then I pumped like crazy. I didn't realise just how much I would have to pump the lever but with the pads pushed right back there was a lot of travelling for them to do. I had to top the reservoir up twice. This made me realise that I had probably had it about right before but just hadn't pumped enough. Eventually the lever firmed up a bit and I could lock the wheel. The lever is tied up at the mo and I'll see how that goes, but I'm hopeful. Then I did the rear, pumped 30 or 40 times and that has firmed up too. Thanks to everyone who offered advice, and those who even took time to PM me.
rather than pushing the pads back and getting fluid out through the reservoir.........open the bleed nipple and push the pads back the air will come out rather than go all the way up the pipe again. close the nipple top up the reservoir and pump the pads back out, open the nipple and push the pads back in.......etc etc
If you push the pads back, jam them back.......IE make sure they stay back.......even compressed air will push them out again. AL
I've had this on a few bikes, it seems to be when air gets trapped in a loop between calipers - it just ends up going back and forwards. My preferred method is to take the hose off the caliper (start at the left hand one as it is furthest from the master cylinder) and pump until fluid comes out of the line freely. Re fit and repeat for the right hand caliper. The only substantial air is now in the caliper a and can be easily bled out. This works especially well if the system has been fully drained down.
