Ninja 250r 08fi 9000rpm sputtering problem when i drive my ninja and the enginge is cold then there are no problems with getting to the rev limmiter but once my bike gets warm then it starts sputtering at 9000 rpm while driving and i cant get it in higher rpm while full throthle, if i rev it full throttle in neutral then it also sputters but then it can get a little higher in rpm, could it be the spark plugs?? my bike has 23000 km's and i havnt changed the sparkplugs yet, i also drived my bike very fast after breaking in the engine