the 599 I believe is the CBR 600 F3 motor, just updated with fuel injection, and the 919 is like the 900RR with the same
The 599 (in the US at least) was not fuel injected for whatever reason.
They still make it for the European market (Hornet 600) and it has FI now.
The 919 has a detuned 900RR engine..... lower compression, different cams, etc. It has more useable torque for city driving.... err.....wheelies.....
Only 2 more months untill riding season.