I remember the excitement In the months leading up to the release of the zx12. It was code named 'Project 320' as in 320kph, or 200mph. I was riding a zx11 at the time, the bike which for seven years was The Fastest Bike. Kawasakis' answer to the Blackbird and Hyabusa was highly anticipated. Then in the midst of all the excitement came talk of government threats, and a coerced detuning of the zx12 prior to release. After the magazine tests in which the 12 failed to reach 200mph, it was released by some extremely disappointed Kawasaki marketing reps with no further mention of government intervention, and no hint of what had been done to the motorcycle.
I've been riding for thirty years, and I've only bought Kawasakis. I understand how their engineers think. I know the same people who had produced the zx11 would have no problem building a bike capable of 200mph. The zx12 is not only beautiful, but it is a fascinating piece of engineering.
I bought one in April of 2000, and have had one ever since. I have followed the story as it slowly came out, a piece at a time. Here is what I learned.
The 12 engine architecture matches that of the ZX6 and ZX9 of that era. This implies that the dyno curves of these engines should show a great deal of similarity. They do not. The power and torque curves of the zx12 fall off much quicker than they should, and the implied peak horsepower is never reached.
Tuners around the world quickly established that the diameter of the exhaust downtubes were restrictively small. Was this done to slow the bike down? I don't know, but I do know that few if any production bikes show as large of a power increase over stock as a 12 does by simply fitting an aftermarket full exhaust with appropriately sized downtubes.
With this simple mod, 12's were very close, but not quite at 200.
A second clue came out some time later, when tuners were becoming more adept at unlocking the ECU map. It was learned that the air & fuel maps continued on for 600rpm past the indicated 11,500 rpm redline.
Back in 2000, when the 12 was released, the metallurgy and finish of its' rotating assembly was state-of-the-art. Forged this, carburized that. This, plus Kawasakis' historic preference for making more power by spinning a smaller engine faster lead me to believe that the redline of 11,500rpm is at least 500rpm less than what the engineers specified.
The final clue is that the engine air intake has a 2mm reduction in each of the four velocity stacks. Now this could be to maintain mixture speed at low rpm, but I don't think so.
I believe that if you negate these three problems, then you will have a bike that performs as it was meant to. Of course this is all speculation but I think it is pretty close to the truth. This I do know - I LOVE riding my 12, think I'm going to go out & take a spin now!