Need help mori seiki sh403

good day to every one.
i have a problem with a mori seiki sh403 msg501
i can not change the rapid feed speed.
i have tried changing the parameter 1420
but it doesnt change phisicaly at the machine.
do you know if there is another parameter to change it?
or do you know if i have to change other thing in the custom screens?
my problem is that with the maximium speed i have variation on my parts on the axis Z.
if i select rapid feed at 25% with the button on the panel the parts
are ok.
i want to decrease the speed only to the axis Z.

thanks in advance.