Got a 2009 crf450r for a steal, ran hard now it seems to cut out when it gets hot. Fire it up, it idles and warms up fine, take off and it screams. A few minutes in it starts to cut out. I put new air, fuel and oil filters in it. I just put a new spark plug in it and the old one looked like it had ran rich. Anyone else had that problem or have any ideas?