Using mecanim for a character on a motorbike

I'm struggling to get my head around exactly how to use Mecanim (or when to use Mecanim) and I was hoping someone could point me in the right direction.

Essentially what I'm looking to do is create a number of animations of a character on a bike (using Maya), which I'll then import and use in Unity. However, the character will essentially be a mix of humanoid and bike - how do I approach that with Mecanim?

Additionally I'd like to ragdoll the character for crashes etc - can I setup just part of the game object (i.e. the human on the bike) as a ragdoll?

Basically I've setup some animations as 'Legacy' but I understand this is being phased out and I'm having a hard time understanding how to do the same thing with Mecanim.

Thanks for any help!