[notunderweight]

Hey all,
I just bought my first bike a few months ago, and have been learning to ride/wrench on it. It's a 2006 ninja EX250F.
About a week ago, I was out riding (like, an hour in) when the engine began to bog HARD above about half throttle. Like, unable to rev past it regardless of gear position. After checking the carb hoses and fuel levels, I went ahead and replaced the petcock vacuum line and fuel filter. It helped a little, but the bike still bogs above 5k.

THINGS I'VE DONE
- Changed petcock fuel and vacuum lines
- Cleaned air filter and checked airbox
- played with the idle screw (this helps the issue, but then I'm idling at 3k.... not ideal)

THINGS I HAVEN'T DONE
- Fixed it
- Changed any gaskets
- touched the carb other than the idle screw
- drained gas lines

THINGS I'VE NOTICED
- engine has more power when throttle is at 1/4 than 1/2
- exhaust smells a little different (i think?)
- adding choke helps
- no trouble starting, with or without choke
- I am at 5300 ft ASL
- head gasket looks a little iffy



Any ideas? What should my next step be? Should I just give up and find a good mechanic? Spray carb cleaner at it every time it acts up?
Thanks,
Jake