Hello, I would like to share some things I've learned to make it practical to work in animations with biped. If you want to create a kiss, it's easier to make it with a biped with a small head. So you can resize the biped's head in a few steps.
1. Dowload biped here:
http://imvudeveloper.altervista.org/blog/files-3d-max-forniti-da-imvu/ -bipedRig_Basic.Max-
2. Open 3Ds Max and then merge your biped
3. Select bone called head and select button Scale Tranform Type-In

4. Put on Absolute Local the value "55"

5. Save in your hard disk as "Biped resize head" or how you want