Zx9r float valves

How long did the bike sit with gas in the carbs without being run?

Probably 2 to 3 months.

hrm, doesn't sound long enough for the gas to go bad again. However, if the carbs have gone green before, they go green much quicker each time after that.... I would recommend re-cleaning the carbs - complete tear down and reassembly, and in the future, if the bike is go to sit for longer than 2 weeks, make sure to get some Sta-bil or seafoam in the tank, and take the bike for a ride to get all the chemical goodness in all the appropriate orifices...