i was always making motocross scenes in a program maned endorphin(i really recommended)
Endorphin is a dynamic motion synthesis software package developed by NaturalMotion. Endorphin can be used to generate computer simulations of large numbers of independent characters interacting with each other and the world according to brief scripts or 'behaviours'. It combines physics, AI, and genetic algorithms to create realistic animations. Unlike Euphoria, also developed by NaturalMotion, Endorphin is not an engine, but a 3D animation tool for Windows PC.

i have made scrubs, backflips, 360, and som non mx stuff
its free for fun use(non-commercial use) the commercial for Pepsi the glue boy was made in this software
hop u enjoy this topic!!!