Reversing the X axis
To properly reverse the X axis on a Mori, you need to reverse the pulse coder feedback signals and also the armature wires to the X axis motor.
Reversing the armature wires is pretty easy (the DC current to the motor), but reversing the X pulse coder requires that you swap 2 pairs of wires in the pulse coder cable. If you reverse the armature without reversing the pulse coder feedback (or vice-versa), the motor will simply "run-away" to the limit switch, so do this carefully. Sometimes, there are 4 armature wires in a single cable, two of them are + and two of them are -, so you have to reverse both the + wires with both of the - wires.
In the pulse coder cable, you have an "A" pulse and a "Not A" pulse (the opposite polarity to the "A" pulse). You also have a "B" pulse and a "Not B" pulse and a "Zero" pulse and a "Not Zero" pulse. The zero pulse is the 1-pulse per rev signal used for zero-return.
Swapping the "A" pulse with the "B" pulse and swapping the "Not A" pulse for the "Not B" pulse should do the trick. There's no need to swap the zero pulse signals because they will be the same regardless of which direction you're going.
After swapping the armature leads and the pulse coder signals, the motor will run in the opposite direction when you press the "+X" jog button. The feedback must agree with the motor armature. If everything is done right, the position display will still show a + motion when you press the +X jog button, but the servo will run the opposite direction.
NOTE: Most Yasnacs and Fanucs do not have "Tach generators" in the motors. Instead, they use the pulse coder feedback to generate a tach signal. If your machine has pulse coders in the motors, then you don't have tachs to worrry about. If your pulse coder is OUTSIDE the motor, then you will have a little tach-generator inside the motor. If this is the case, you'll have to reverse the tach leads as well.
After all this is done, you will have to find the parameters that determine the DIRECTION of zero-return. This parameter just tells the control if you are going to zero-return the axis in the PLUS or the MINUS direction. Your machine is probably set to MINUS, and it must be changed to PLUS, otherwise when you try to zero-retun the X axis, it won't see the cam-operated zero-return switch correctly.
Good luck!