[schmdty420]

I recently bought a used 03 Ninja 250 w/ 14k miles on it. This is my first bike and to me seems like it runs pretty good, but I have noticed a few things that don't seem quite right...First off; the bike has to be at about 3/4 choke to start, and stay there for a few miles of riding or the bike will die. Second; during its "warming up" period (while the choke is on) the RPM's fluctuate up and down. Not by much, but around 1k. Third; I've seen tons of videos where people take off on their Ninjas and easily rap it up to 11k RPM through all gears...My bike sounds like it's gonna explode at around 8-9k, through all the gears. especially 1st through 4th, and sounds to me likes it's revved very high at 9k in 5th gear.
The bike seems to be in excellent shape and the previous owner said it was well maintained, but who knows really. I tried to contact him about whether the valves had adjusted recently or not, but no response...
Could it be the valves are tight? Dirty carbs? I've tried SeaFoam with some luck on performance, but not with the idle. I'm pretty mechanically inclined so tearing into the motor isn't an issue for me. I'm just kind of at a stand-still right now. I don't know whether to tear it down and check out the valves or clean the carbs or both...What do you all think? Any advice would be great. Thanks everyone for any help.