was riding for like 3 hours then my 400ex when ever u went passed half throttle would bog really bad...it ran for another hour jus to get home but it wouldnt let me go past half throttle..i jus cleaned the carb 2 rides ago so i dont this its that

 

what does your spark plug look like?

 

i would say check your floats. i had a problem just like that in my old kfx 400 all the time. what i used to do was get into 5th gear then down shift into 2nd and from the down shift the quad would be in such a high rpm that it would fix the floats! i hope this helps