From the manuals ...

Resetting User Memory to the initial factory settings
The original factory settings of this synthesizer's User Memory can be restored as follows.

NOTICE: When the factory settings are restored, all the Voice, Performance,Song, Pattern, and system settings in the Utility mode you created will be erased. Make sure you are not overwriting any important data. Be sure to save all important data to your USB flash memory device before executing this procedure (page 60).

1) Press the [UTILITY] button then the [JOB] button to call up the Factory Set display.

2) Press the [ENTER] button.The display prompts you for confirmation. To cancel this operation, press the [EXIT] button here.

NOTICE: When entering a checkmark to the box of Power On Auto Factory Set and executing Factory Set, the Factory Set operation will automatically be executed each time you turn the power on. Keep in mind that this also means that your original data in Flash ROM will be erased each time you turn on the power. Therefore, the checkmark of this box should normally be removed. If you remove the checkmark of this box and execute Factory Set, the Factory Set operation will not be executed when turning the power on the next time.

3) Press the [ENTER] button to execute Factory Set. After Factory Set has been completed, a "Completed" message appears and operation returns to the original display.

NOTICE: For Factory Set operations that take longer to process, you will seethe message "Now executing Factory Set..." during processing.While such a message is shown on the display, never attempt to turn off the power. Turning the power off in this state results in loss of all user data and may cause the system to freeze (due to corruption of data in the Flash ROM). This means that this synthesizer may not be able to start up properly, even when turning the power on next time.