My 2008 is a cold-blooded ogre
I was having trouble starting my stock 08 Ninja. Again, that was my STOCK Ninja, with factory exhaust. It seems every 08 suffers from this. I could not use my choke at all. It would start ok when the weather was warm, but as soon as it turned colder it would start very weakly and sputter out. Using the choke made the bike stall immediately.
Everyone told me the new 08 was a "cold beast".
Some will tell you that shimming the needles will fix the problem, but it won't. Shimming needles only affects midrange, not idle start up.
An acquaintance is a licensed Kawasaki mechanic (who is smart enough to no longer work at a dealer). I let him at my bike. He took the carbs out and drilled out the plugs barring access to the fuel mixture screws. They were set at 1.5 turns and 1.75 turns from the factory. He turned both to 2.5 turns, and now the bike starts great and I can use the choke perfectly. My bike is completely 100% stock with stock exhaust. This is the way it should have been dialed from the factory.