Anti-theft Radio... How to reset?

[TUSE]

My Dad just bought a 91 K100LT with the factory BMW radio (apparently with the anti-theft option). How do you reset it (It turns on, it shows some numbers (654 and a little 3) and the speakers crackle a little when her turns the bike on, but the radio does not seem to want to work. He thinks that with the tape deck he can barely hear something in one speaker (of-course, now he can not get his tape back out).
Is there a code, if so, where/how do you get the code and how do you input it?

Thanks for any help,

TUSE

[mobygrape]

The bike should have come with the radio code on a card with the owners manuals. If there isn't one, a BMW dealer can input a code number found on the radio chassis into the BMW dealer website and get the proper four digit code. If the wrong number is entered, holding down the "band" button will clear the display and allow the code to be entered again.