[Downeaster]

How important is it to have the bottom bracket shell chased and faced before installing a new bb?

 

[13pumps]

If the frame is new and never been faced it is very important. If you are replacing a BB then it should be fine

 

[Ratt]

Depends, on highend frames usually this is all done

How important is it to have the bottom bracket shell chased and faced before installing a new bb?

If i see paint anywhere around or in the headtube/bottom bracket I usually get things faced but since i can't get it done for free (used to work in a sporting goods store) anymore i have been known to clean the paint out with a razor blade and "chase" the threads with a steel BB. But Yeti frames definitely do not need to be done, check out the Tour, click on "Frame Prep".