Take the reservoir off the bike and use a small screwdriver or the like to push the piston in as far as possible.
Then crack the banjo at the reservoir to bleed the line.
It is important that you then get just the right angle on the hose when you are finished bleeding from the banjo.
If its too low the swingarm will raise up and knock the banjo loose and if it is too high the exhaust will overcook the porridge.
Other thing to check is that the master cylinders piston seal isn't damaged, if above doesn't help you.