After pulling around our new 5er I noticed loud cluck when
stopping and then another loud cluck when pulling away from
a light...sounds like some play or slack in the kingpin and the locking horse shoe. Any ideas?

 

Check to see if there is any play between the lower Turntable Cam Arm and the Nylon Block. If there is then you need to remove the play. ;D

 

how do you remove the play?
Turn that big middle adjustment bolt?

 

Yes, you need to adjust the big bolt which has the lock nut. Loosen the lock nut, then tighten the bolt finger tight. Then tighten 1/2 turn more and retighten the lock nut.