Kourtney Kardashian and BF's Relationship Is Smoothie Sailing

Kourtney Kardashian doesn't have a new baby like most of her sisters, but she's still rocking an ear-to-ear grin, courtesy of BF Younes Bendjima.

They were giggling like a couple of school kids while juicing up Monday in West Hollywood. The mom of 3 and her 24-year-old dude kept it chill ... hanging outside for a few minutes and chatting ... before leaving in separate cars.

Younes seems to leave chicks smiling at juice stops on the reg.

Based on her crop top and exposed abs ... we're positive he hated to see Kourt go.