This is in three parts. Firstly the factory OS needs to be reloaded and then the sound banks will have to be restored from ROM. Please note that it is unlikely that the factory OS should ever need to be restored. Any problems which require a "reset" can usually be overcome by restoring the global data and/or the sound banks 1&2.
K-Station Factory installed OS Restore
Turn on with buttons 8, 9 and 0 held down. The screen should show "Original OS?" for factory OS. Press the write button twice to restore the OS.
K-Station Bank Restore
For a K-Station to be completely reset, Bank 1, Bank 2 and the Global data need to be restored individually - there is no total data restore. The init banks 3&4 are not stored in the K-Station ROM. When restoring banks of factory programs, the program entered before the utility menu was entered selects the bank the restore will go to - i.e. if program 152 was selected, B1 or B2 will be restored to Bank 1. Select Program 100.
Enter the Global mode and ensure that the memory protect is turned off. Enter the utility menu and find the restore page. The options are "1 Program, 1 bank, and Global D" Select 1 bank as the option to be restored. Press the write button. The screen will show rest? B1
K-Station Global Data Restore
Enter the utility menu and find the restore page. With Global D selected, press the write button twice to restore the global data. The K-Station will restore the global data. This will automatically write protect the K-Station as this is one of the restored global settings.