What's the tire pressure? Too much pressure will have the tire bouncing like a basketball, particularly on bikes with raked out forks.
I'm not condoning it, do so at your own risk, for off road use only, don't try this at home, but, I run 15-20 psi on bikes with extended/raked front ends. Less weight is carried on the front wheel, the further it is from the center of mass. Add to that the fact that raked out, or worn out, sticky forks, are generally ineffective at dampening the vertical movement of the wheel. Airing down the tire allows it to absorb more of the movement that starts it bouncing.
I'm rambling, but you get it.