07 kx250 4th 5th gear hesitation problem

[Krhonn]

I have a 07 kx250 and it seems to hesitate or start to run out of fuel when shifting to 4th and 5th gear. The bike runs like a raped ape 1st-3rd gear. I can hold it wide open in 3rd gear all day long with no problem but as soon as it shift to 4th it hesitates. Adjusted the float but it didn't help. Not to sure about jet and needle placement. My father has worked on my bikes for the past 18yrs and we've never ran across this kind of problem. We've found water behind the cover with the stator and it seems there's been a lot of moisture in there for some time do to the looks of corrosion. Any suggestions on what this could possibly be would be appreciated!

Thanks in advance

[motopunk]

water behind the stator cover?? oh oh thats bad ..   it could damage stator or cdi or both .
  with a little luck you can dry the stator and the problem is away... 

in the future you should istall a good gasket on stator cover ..or open it after any water cleaning and make sure, the stator is dry and can work properly..