Do as Grant states but for what it's worth put the RGS on the side stand, remove most of the hydraulic fluid from the reservoir but keep enough so the level still covers the bottom of the reservoir and not allow air in to the intake. This is to prevent spilling hydraulic fluid when you remove the master cylinder from the handlebar. Remove the master cylinder and rotate it with the lever pointing as high as possible so that the air can move upwards out of the banjo. Now the important part, gently squeeze the lever only a small amount so that the port is just opened, repeat this several times slowly and you should observe a stream of small air bubbles. Top up the reservoir if required.
I got this tip from Piet and had a rock solid front brake on the RGS within 5 mins.
HTH
Ian