Following Sean Collier's amazing performance at the Glen Helen national last month, the guys at Motocross Action magazine hit us up with a simple request—the opportunity to comparison test Sean's race-winning KX500 and his fire-breathing fully modified KX450F. Needless to say, we didn't hesitate to say yes, and met up with MXA at LACR for a day of testing. The video gives you an excellent glimpse into what was modified on each bike, but be sure to pick up the next issue of Motocross Action for the full story.