Yes I set up the various speed constraints listed in the STAR. Since my post I tried the flight in reverse. I flew from LAS to LAX and everything went fine. I had the speed set up at 180 for particular waypoint and the model reacted fine. I had only one instance where the speed jumped to a higher speed. I do believe when the model goes to a steady altitude during an arrival the fmc reverts to cruise speed no matter what the alt is. I had the speed set to 240 on approach to lax rwy 25L. The alt between wypt LUVYN and Krain is 10000. It was at that time the model jumped to cruise speed (319). Maybe be an fmc glitch.