I have had big problems in the past, mainly with the twin piston AJP kit fitted to modern bikes.The bleed point is not at the end of the fluid path, the second, or inboard piston, is past the bleed nipple, so air in there is sometimes a complete B*&*&*d to get out. The local scooter shop gave me a tip that works when you have tried everything else. The scooter reference might sound a bit strange, but lots of modern scooters run with AJP brakes, and he works with them every day, so I listened.
When you have given up trying to get the last bit of air out of the calipers, take it off the bike, remove the pads, and pop the pistons out of the cylinders.Split the caliper, carefull with the little O ring between them. Clean everything up, and fill the cylinders with brake fluid. Enter the pistons back in, forcing a little bit of fluid out of the linking hole. Bolt up the caliper halves, and again push the pistons in just enough to force fluid out of the bleed hole, and brake hose connection point. Fit the pads, bolt the caliper to the bike, fit the hose, but leave it not quite tight. Again push the pistons back in the caliper slowly, allowing fluid to come out of the hose connection, then nip that tight, then the same with the bleed nipple. Continue now with normal bleeding . It's never failed me. Good luck.
