I just had a new crown..every time i floss it smells bad..wondering why?

I would recommend returning to the dentist to have the crown and gums evaluated. A crown that does not fit perfectly can cause a buildup of odor producing bacteria. If your dentist does if fact find an issue with the fit of your crown, it would need to be replaced. Another important factor to consider is proper oral hygiene. Good luck and I hope this helps. Follow me if you have more questions.

There are a number of reasons you get a smell after flossing  which can be related or not related to your new crown.  Did you notice this before the new crown was done?   I would go back to your dentist and tell him what's happening so he can evaluate your gums around that crown.