The 2001 engine is no different (power wise) to the later engines. Phil
Here's a summary of the various year ZX12R's;
The ZX12R was launched in 2000, this particular model is known as the A1 model. This was the only model that is derestricted for top speed as standard. All later models are restricted to 186mph, although models upto 2003 can be de-restricted with a Muzzy Bonneville Box.
The A models made in 2000 & 2001 (A1-A2) have a lighter crank than the 2002 -2005 models (B1-B4). The lighter crank helps the engine to spin up quicker, but it also increases engine braking. Kawasaki beefed up the crank in the B models which makes them smoother to drive with less engine braking, thereby maintaining engine speed through corners off the throttle.
In 2001, the ZX12R got different cams and different throttle boots along with the electronic limiter (186mph). All else remained the same. The 2001's were said to make the same top end power but have a little more grunt in midrange.
In 2002, the ZX12R got a major revamp. These are the 2nd generation 12's (The B models). The important engine upgrades for BEC's are the heavier crank and oval throttle pulley.
In 2003, the engine remained the same.
In 2004 the ZX12R got a few more upgrades:
Secondary throttle blades (probably slows the airflow but smooths out throttle response)
New fuel/timing map in the ECU and 32bit instead of 16
2005, same as 2004.
The differences between the A and B models is said to be definately noticable. The B model is smoother, and easier to control on the throttle mid corner. The A model was however more 'raw' but not any quicker.
You'll not go wrong with any model of ZX12R but IMO, the 2004 & 2005 engines are slightly more refined.
[Edited on 14-12-08 by Hellfire]
