apparently the answer to my original question is: yes
Bike is a '08 ABS and has 75 000 miles of tons of curves, city, and highway droning. All of it.
Small summary of what's been done:
- brakes overhauled: callipers and master cylinder disassembled, cleaned and new seals. Everything looked in very good shape, no scratches, wear, etc.
- new brake lines: I went with stainless steel
- new brake discs and pads: I got EBC.
And yet... The bike brakes 100%, that's not the issue. But the brake lever has a dead stroke when I first pull it. If I release and pull again rapidly, the dead stroke is all but gone and brakes operate like new. But if I release the lever and wait, say, 5 seconds to pull it again, it'll have the same dead stroke. As it happens, while they were looking at it at the workshop I noticed that the '16 Z1000 seems to have the same master cylinder. I pulled it, and my hand perfectly remembers the perfect feel of that brake, as it was on my GTR when I bought it.
Bad news: the dealer doesn't know what to do. I told him that he has a blank check, now go fix my brakes, but he stared at me without an answer, until he said that he doesn't know what else to do. I'm not pissed at him because everything done so far to the bike had to be done anyway, so no hard feelings and no wasted money.
Anybody has an idea? The mechanic thinks that the only thing left to try is a new hand brake assembly, master cylinder and all. Since I've been a very good customer for 7 years he offered me to take the assembly from the Z1000 that they have for rent and put it in my bike for a test, before ordering the new part (350USD).
What do you guys think? I'm starting to loose the pleasure of riding the bike. I'm really feel like I'm running out of options.