If you have a split keyboard e.g. Bass and Piano, is it possible to route them to individual audio outs ie Bass left Piano right?

The Motif XS does not have to be SPLIT for you to send PARTS to separate outputs. In other words, you can do it for Splits or for LAYERS - the OUTPUT SELECT assignment is independent of where the sounds are assigned to be triggered.

The OUTPUT SELECT parameter is a PART parameter found in PERFORMANCE mode and in SONG/PATTERN MIXING modes.

Press [EDIT]
Press a numbered button [1]-[4] if using a PERFORMANCE, [1]-[16] if you are using a MIXING setup
Press [F1] VOICE
Press [SF2] OUTPUT
Highlight the OUTPUT SELECT parameter
Press [SF6] LIST to view a list of the available OUTPUT options…

If your Piano is PART 1, set the OUTPUT SELECT = asL Assignable Output LEFT
The Bass in PART 2, set the OUTPUT SELECT = asR Assignable Output RIGHT

Connect your Motif XS’s Assignable Outputs to your separate sound system devices.