Bleeding brakes like many things is a skill and with some modern master cylinders being mass produced sometimes rough areas within them can catch and air bubble which you simply can't remove with normal bleeding procedures. In these cases you can use our handy 'trade secrets' which may well help.
1 Tying the lever back overnight
One way to rid any last remaining air from the system is to tie back the lever over night. Firstly remove the master cylinder reservoir cover BUT and then balance it back on top of where it should be fitted so that moisture in the air does not contaminate the system overnight. Then pull the lever in as hard as possible and cable tie it in the ON position (brake lever pulled right back to the bars). Leave this overnight and in the morning release the lever and your brakes should feel fantastic - basically the back pressure caused by tying the lever back overnight will have forced any last remaining air out of the system out to the atmousphere and leave you with sharp brakes the next day. Replace the reservoir cap correctly and you are ready to ride.