CB400F Horn Repair
The horn fitted when I purchased bike was not original and missing the bracket that holds rubber strap used to secure wiring loom.
Saw an original on Ebay, won auction, but horn doesn’t work
I was going to bin the horn but thought I would ask if anyone had attempted repair.
Had one reply from Runuv "cut the rolled edge in a couple of places and opened the horn on my 400 I repaired it and put it back together works fine" so thought I would try.
Before dismantling I had found that there was an open circuit between two terminals and even after removing large and small adjuster this stayed open.
After removing the plastic cover ( I warmed with a hot air gun as it was pretty cold in my garage) by gently levering off in slots.
I made one angled cut to folded edge with junior hacksaw and used nail remover pincers to peel back folded edge.
Also used long nosed pliers in the process to allow clamping ring to be removed.
Take care not to damage paper gasket when removing horn plate..
The problem could now be seen, which was corroded contacts.
When power is fed to horn it energises the coil of wire which draws the metal centre inwards.
There is an insulating ring that pushes up against the contacts arm and separates the contacts.
With the power disconnected the centre moves outwards, allowing contacts to close and process repeats until power removed.
I cleaned the contacts with emery cloth and now had a resistance of 1.5 ohms between terminals.
Held horn together and adjusted small and large screws to approx. original positions.
Applied power to terminals and small beep from horn.
Re assembled and carefully folded edge back in place.
Tone and volume are adjusted using the two adjusters on a trial and error basis until you get the sound you want.
Hope this helps anyone wanting to try and resurrect a faulty horn.
