a technics sequence cannot be simply saved as gm2 in this way because the sequencer is triggering accompaniment from preset or composer/custom memory which have no equivalent in the general midi specification using the automatics built into the machine.
First go to menu/sequencer/copy&paste/apc to smf convert and list the accompaniment tracks drum, bass, acc1, acc2 etc into the unused tracks of the sequencer e.g. 9 to 16, making sure sure drums are track 10. Press convert in the screen and all the individual notes of the automatic accompaniment will be written to those tracks you have entered. This procedure clears the apc/chord data so always save as a technics file first so you can go back and play around with the tracks if needed. Now save as gm2 with header and one measure space and you have a midi file.
Even so mostly it will sound worse than the technics sequence because the voices will have been changed to the nearest gm voice, which are generally worse than the technics voices due to limitations in the gm spec. But you can then play around with voices in gnmini or other gm editors.