Bike wont run in high speeds

whyen i start the bike and try to drive it for a while on the road, the bike turns off, (not in the electrical way), and i am having problems starting it again. it happens most commenly in high speeds around 80-90 km/h. i have changed the fuelfilter, and sparkplugs. does any one know what the problem can be, and its not the fuel lines, i have checked them and they are fine. its a gt125r 2007-model

thx for answers