There are lots and lots of threads about this. It seems like you already went through them. But I'll say it again. It's critical that both of the two small holes between the reservoir and the cylinder are open and clear. It'll never work if those are plugged.
kzrider.com/forum/5-chassis/569907-z1r-f...tute?start=20#647373
www.kzrider.com/forum/5-chassis/608766-f...servoir-holes#786303
But even if everything is mechanically perfect, if you have air trapped in the system the master cylinder won't draw in fluid. There are tons of recommendations for this.
One thing you might try is to get a vacuum bleeder, attached to the calipers, and pull fluid though the system. Something like this.
www.amazon.com/HFS-Brake-Bleeder-Vacuum-Tuner/dp/B00NP60URE
www.amazon.com/MV8000-Automotive-Tune-up...eeding/dp/B00265M9SS
That's often good for about 90% of the trapped air. But often you're still left with a bubble. At that point the general recommendation is to let it sit for a day or two.
The idea is that this will let air trapped in the fluid separate, and then hopefully float up to the top to the master cylinder.
And many people say to tie the brake lever to the grip so the master cylinder piston is all the way pushed in. Many people here swear by this. It's possible that a common issue is air trapped in that small space between the two master cylinder piston seals. Pulling the lever in and letting it sit for some time would help to let this area fill with fluid.