Horn

It honks!

It's a standard 12V motorcycle horn. The replacement bike's horn sounded like a strangled cat until I turned the adjustment screw first one way (went silent) then the other (sounded like a horn). You can replace them for less than $10.

https://www.revzilla.com/common-tread/how-motorcycle-horns-work-and-how-to-fix-them 

An adapter (see Additional Cables/Adapters) is used to connect the horn to the 12V Harness.