[greywolf]

It's behind the radiator. Getting the plastics off is covered here.
Fuel Tank Removal How to, 650 & 1000

 

[Irish John]

Thank you sir.

 

[adh6501]

Or, better yet, having found it, disconnect the wires and attach them to a PIAA Sports Horn (or, if you really enjoy attention, a Stebel). Consider your stock horn to have done you a favour by dying prematurely.

 

[Big B]

Or, better yet, having found it, disconnect the wires and attach them to a PIAA Sports Horn (or, if you really enjoy attention, a Stebel). Consider your stock horn to have done you a favour by dying prematurely.

That need a relay "Piaa sports horn?

 

[adh6501]

Greywolf said yes, but I decided that the draw was close enough to the stock horn to get away without one - I don't see any of the warning signs (lights dimming when you activate the horn) that suggest it's overloading the system and therefore in danger of burning out the horn switch. My decision didn't have anything to do with the fact that I really don't understand relays yet....

You definitely need one for the Stebel.