Installing a Stebel air horn on a motorcycle

The wimpy "meep-meep" stock horn on my 2001 Triumph Bonneville, like most motorcycle horns, is pretty much useless at getting the attention of a distracted driver in a car headed right at you. I finally ordered the acclaimed and very affordable Stebel Nautilus air horn (also marketed under the apt name "Ear Cannon" - mine was less than $50 from Aerostich) but when it arrived I realized that this compact device, made for automobiles, was still too big to simply replace my existing horn. No, I had to do what every red-blooded biker does - customize. One valuable piece of information was available on the Web - the idea that the device could be broken down and mounted in parts. In the spirit of giving back to the community, here's what I learned.

Ride safely.

Lincoln Cushing
Berkeley, California

Here is the horn out of the box. Notice the small plastic tab cluster above the round horn section - this will need to be pried back to slide the air pump from the horn unit. I also sawed off the mounting ear, which was on the pump's upper housing on the left. Not shown is the relay, which comes with horn.
Let's hook them up.
I carefully drilled slightly into the plastic casing (not too deep, don't want to break anything) and nested a brass air compressor hose fitting in the inlet, then generously applied epoxy.
I used a small piece of scrap tubing to join the air compressor hose onto the pump, using a bit of silicone sealant.
I carved out two slots in the fitting that originally held the pump, and slipped a hose clamp through it. I also trimmed back one of the curved mounting ears for clearance.
Left side of bike view.
Horn installed, hose clamp on top of short section of standard PVC pipe foam insulation. The foam accomodates for the curvature of the horn's plastic mount, which is a larger diameter than my frame.
My bike wiring may be different than yours; this Bonnie has a horn that is switched to ground, not positive.
Front fork view.
I disconnected the leads to the existing horn. I left everything intact if I decide I want both horns. The lead I wanted was the purple one. I added a wire running back along the chassis.
The tiny relay wiring diagram that comes with the horn gives four options - with and without existing horn, positive or negative actuated switch. Get a magnifying glass, this is about 4X original size. I did not cut my existing horn wires as indicated.
Underseat view.
Here it is, ready to go. Don't laugh at my wiring. If you are fussy Aerostich sells a wiring kit. I added a connector between the pump and the horn - I may want to add a fitting there to let me add air to my tires when far from a gas station. My stock seat fits on top of this, but was tight, so I tweaked the plastic panel under part of the seat to better accommodate the pump.

It is LOUD.
I promise to only use this power for good. Yeah...
Postscript 6/1/2013: Some websites say that the manufacturer asks that the horn be mounted vertically, apparently to reduce uneven piston wear and thus premature seal failure. Since I can't do that, I'm going to try and occasionally squirt some lubricant into the air intake hole (that's the opening on the top of the pump cylinder, above, right next to the hose fitting).

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