I like many others have always found the brakes on the ZZR a mystery. Go to the forums of different Kawasaki websites and there are numerous threads regarding the power and bleeding issues associated with this subject.
Many recommend changing to GSXR calipers, amongst others. People complain that when new pads are fitted and the system is bled they work well for a short time and then the lever starts heading backwards towards the handlebar. It has been a mystery for many (me included). Tests from the period compliment the braking and state how positive the brakes are. So why do so many have issues?
I like others have just excepted it. Sure, there was so much lever movement that it would send most modern sports bikes riders running for the weeds but hey, we are used to it and it never stopped me from going at Mach 9 whenever the chance presented.
But no longer!! The mechanic who now works on the bike if I cant stated that it was not acceptable after taking the bike for a test ride and he was determined to fix the issue. "Good luck" I said, confident that he would not be able to fix an issue that has persisted with so many ZZR's for 30years.
He took the calipers of, and started measuring just about everything that could be measured, checking alignment, the mounting surfaces, and after it all he just said "they are misaligned" He then proceeded to shim a couple of the mounting points(it was a little more long winded than that) and then announced "problem solved"
I was skeptical, until I rode it, Wow! I have now been riding for a month and they are perfect. 1 finger braking from highspeed? No problem! Hardly any movement of the lever required. So powerful that if you wanted to perform a stoppie, it would be easy.
So how the hell does this happen. Well having checked everything he believes there are slight manufacturing variances and that the calipers are slightly misaligned. This causes the caliper to exert more pressure on one pad, this wears fractionally faster than the other. This is turn means that there is more pressure required to bring both pads into contact. This causes more brake fluid to be used to move the pistons, hence the increased travel of the lever.
By the number of people who write in about their brakes it would seem to have been a common manufacturing error. Indeed, my ZZR D3 that I had in the 90's also had this problem and the Service center never fixed it. They would work on the brakes, declare it OK, and then a week or so later the lever movement would start increasing.
We all know about the misaligned oil pathway that has caused some ZZR's to blow the No 3 con-rod so it is not unknown for errors to make it too production.
Whatever the cause, I am now riding around with the best brakes I have ever had in all the many years of riding the beast. Happy Days!!