Hot models make any picture better!
C&C per req:
1. Good exposure on her skin and the bike; a shame about the blown sky. Always make sure that the subject is looking toward you (not necessarily right at you, but toward you) unless there's a reason for them not to. In this case, it looks to me like she's trying to decide what to have for supper. As well, I think a more open crop on this one would have helped, as the motocycle portion is so small that you can't be 100% sure that it is a motorcycle until you look closely. Lastly, always make a last-minute check for things like the bit of bra and strap that are showing on her left side.
2. Better pose & expression, but still not enough of the car. A little diffuse fill light around her waist would have helped as well.
3. This one doesn't work; too much DoF (the background should be at least soft vice sharply focused) and the other model and car are competing for the eye's attention.
4. I think this might have been better as a 3/4 profile rather than side-on. The lighting is a little harsh, and the cop a little too tight on the front; perhaps it would work better in landscape aspect.
5. Not really liking this one too much; she's trying to hard with her pose (and doesn't look like she's really into it). As well, the dark area lower right draws the eye away from the bikes and the girl.
6. This would have been a nice one if the model was cooperating. She too looks like she's trying to remember if she already picked up her dry-cleaning or not. I think perhaps just a bit brighter on her front and the motorcyles.
Overall, some good work. Most of the issues I have with these images centre on the models, and in this type of shoot you can't really 'direct' them the way you would in a commerical shoot.
Just my $00.02 worth - your milage may vary.
~John