Topic: 78 cb750k Horn inop.

[grwmotocycles]

A few questions on the horn, # 1 I have heard they will not work without the bike running, # 2 the buttons are junk, Mine does not work at all and I would think 12V to the horn would make it yell!!  Still inop.  I am going further into this but just thought I would try to get a few suggestions.    Thanks Geno

[mark]

#1 key on anyway. #2 maybe so but most work.

12v direct to the horn should produce a healthy beep. There should be battery voltage at the black wire with key on; the light green should ground with the button pushed in.

[bryanj]

Some years are permanently grounded and powered via the button,

put two seperate wires direct from battery to horn and it ought to beep, if not they can sometimes be adjusted otherwise replace

[grwmotocycles]

Thanks for the info.  I have tried the direct wires from a battery charger and no sound, but I did not try to adjust.  What is weird is I have a set of duel horns from a 79 F model and they do not work either, even direct hook up.  Maybe the both just need adjusting.

                    Thanks Geno

[Patrick]

Sometimes after they sit for a long time these old horns kind of crust up inside. There is an adjustment screw on the back of the horn body. You can sometimes make them work again by turning that adjuster just a little to break things loose. That's worked for me a few times. If you want to make the horn work when the key is off run a wire directly from the battery through a relay to the switch and the horn. I did that on my K5 to allow me to use louder than stock horns.

[goon 1492]

Or take the wires off the horn and hook up a test light to it, it should lite up when you push the horn button.
That's also if the button is working like you suspected

[NitroHunter]

I saw a bumper sticker that read "Horn broken - watch for finger"
 

[grwmotocycles]

The finger deal may work but that is usually after you are off the road and trying to hang on with two hands !!