Recently got a 2003 ZZR600 with 12k miles on it. I rode it a bit but never really opened it up due to not knowing the condition of the engine/oil etc.
Well I finished having a lot of work done to it, spark plugs oil change, brake fluid, air filter, coolant, chain adjust, carb sync (based on 3rd carb), valve job (all intakes were out of spec and all exhaust was almost out). It rides great but iv'e noticed that from about 8k up it feels a little lack luster. Compression is well within spec.
I dont have any hard performance numbers but it seems to accelerate about the same from up to 7k rpm as it does after 7k rpm. Considering peak power is well above 7k i have concerns. Thanks.