They are alright, but there is nothing special or impressive about either one of them.
For the second shot you need to consider a more interesting angle...Get down low on the ground and shoot it, maybe from behind him. I have some experience shooting dirt jumping (bmx on mountain bikes basically) and I have found that you really have to get into awkward positions alot of the time to get good shots. Sometimes you have to put yourself or your gear at risk, but how much you do so is up to you.
I haven't had a chance to shoot it much since I've gotten better at photography though, hopefully I'll be taking a trip to a place called rays mtb in cleveland ohio soon. It's a 120,000 sq. foot indoor mountain bike park. I go mainly to ride, but I'm really looking forward to taking photos this time too