by: Paul Duffy and Eskort
with inspiration from Toreador's thread


I recently bought an FZ1. It is a great bike to ride, but the horn leaves a lot to be desired. Let's face it, if you can't hear the horn yourself, how is that guy in the car next to you with the cell phone planted in his ear going to hear it? This horn, with its 139db output, will fix this problem.

I was at my favorite tool store the other day (Harbor Freight) and saw a compact, dual note, air horn for $35. This one had a couple of chrome covers and a sticker that said "Bad Boy Horn," but was otherwise identical to the Nautilus air horn available on the internet. There are a lot of criteria to meet to mount this horn and get best performance:

  1. We'd like the output of the horn facing forward, and relatively unobstructed.
  2. The manufacturer requires it be mounted within 15 degrees of vertical.
  3. We'd like to prevent any interferences with the suspension and steering through the full range of travel and turning angle.
  4. We'd like to keep it as much as possible out of sight.

While some folks have tried to stuff it into the original horn location, Eskort and I thought that it would be better to put it where the alternator rectifier/regulator is located, and move the rectifier/regulator to the original horn location. This avoids any problems with the horn interfering with the fender or steering. The regulator position is also reminiscent of 1960's British bikes which often had fully chromed regulators in this position. As with the British bikes, this gets the regulator in the airstream and allows it to run cooler during operation. It is relatively easy to do and works great.

Items Required:

The terminals, tie wraps, wire, fuses, and fuse holder can be obtained at your local auto supply store (e.g. Murray's or Autozone). Air horn is available on line here, or at Harbor Freight. Bracket material can be obtained at your local hardware, Lowe's or Home Depot.


To start, disconnect the ground side of the battery. You do not want to work on a powered electrical system.

We popped the chrome covers off of the air horn, removed the sticker, and painted the assembly black. On the Nautilus horn, only the motor/pump section requires painting. We did this so that the horn would not be too obvious behind the fairing:

After removing the inner fairings, here is the original rectifier and horn location (fairing is removed for clarity of picture only - not required for mod):

Lift the front of the tank and disconnect the regulator. If you haven't already done Eskort's connector modification, this is a great time to do it because we need to extend the lead length on the regulator/rectifier. Remove the regulator and bracket assembly as shown in picture above, then remove the regulator from the bracket. As illustrated in Eskort's connector mod, remove the connector from the regulator harness and add wire (14 AWG for the white wires, 12 AWG for the red and black wires) to extend the overall harness length to 33".

A note here about splicing wires, universally applicable - to get a good in-line splice:

Now, back to our project - Remove the bracket and cut off the regulator mounting arm, then drill a hole for the bolt that will hold the air horn in place. The bracket will end up looking like a mirror image of the fairing bracket on the RHS of the bike.

Use the plastic spacer that comes with the air horn and mount it to the modified bracket. It should look something like this:

Disconnect and remove the original horn and bracket. The blade connectors fit on the air horn relay in the new installation. Fabricate a bracket to hold the regulator in the old horn location. We used a piece of bar steel, drilled and countersunk two holes to match the original horn bracket, and drilled and tapped two holes to match the regulator mounting holes.

Alternatively, you could fashion a sheet metal bracket, bending up the sides to provide clearance to the mounting bolts.

Mount the bracket, then the regulator with the wiring down. When done, it should look something like this:

Wire routing is important to avoid interference and water management problems. This next series of pictures shows the routing for the regulator harness. Note that the regulator is mounted so that the wires are pointing down, and there is a drip loop below the regulator. This minimizes the risk of the potted regulator module of "breathing in" water through the wires as it heats and cools in normal operation. Use tie wraps to secure the regulator harness to the lower triple tree clamp and the main harness. Note its position relative to the other cables and wiring coming off of the handlebars:

The two leads from the horn switch on the handle bar follow the same route as the regulator harness and connect to the relay coil. The relay is tie wrapped to the main harness, just below the regulator mounting tab welded to the frame. See following picture. Attach a ring terminal to the in-line fuse holder, and splice a red 14 gage wire long enough to run from the positive battery terminal, following the main harness, to the relay contact terminal. Attach a 1/4" female blade terminal to this end of the wire and connect to the relay. Temporarily mount the air horn (already on its modified bracket) to the welded tab on the frame. Attach a 1/4" female blade terminal to a length of dark-colored 14 gage wire and connect it to the other relay contact terminal. Run this wire to the positive terminal of the air horn, attach a 1/4" female blade terminal (right angle terminal will minimize sightline), and connect it to the air horn. Finally, attach a ring terminal to another length of black 14 gage wire to go from the negative battery terminal to the negative terminal on the air horn, also following the main harness. Attach a 1/4" female blade terminal (right angle preferred) and connect it to the air horn.

The last step is to add the suppression diode. Whenever you have an electrical device like a motor (inductive) that is being switched off, there is a large negative transient voltage (200-500 volts) generated. This causes arcing across relay or switch contacts, causing them to wear out prematurely, and can also cause electro-magnetic interference and failure of electronics. The suppression diode suppresses this transient. This diode gets soldered between the leads going to the air horn. Tape the leads together in order to maintain their relative position. Disconnect and remove the air horn, noting which lead goes to the + terminal and which goes to the - terminal. Use a sharp knife to remove 1/4" of insulation from each of the leads, about 1" apart. Now solder the diode between these two spots, with the banded end of the diode connected to the + lead. Then wrap it with electrical tape.

Eskort chose a different route for the suppression diode. He mounted it to the motor terminals of the air horn way up against the plastic housing with properly sized insulation on both leads. Once mechanically mount with a loop around the terminal at its base, he soldered the diode lead to the terminal. This is a bit more difficult to implement because the lead connection must be flat and you must quickly solder the leads to prevent melting the plastic base which holds the terminals.

Mount the air horn to the frame, and connect the terminals to the air horn. Finally, connect the leads to the battery, turn on the key, and try the horn. It's a BLAST!

The information presented here reflects solely our personal experience with our motorcycles and is presented for entertainment purposes only. No information presented here is to be relied upon for issues of rider safety or to replace the services of a qualified service technician. Any attempts to follow or duplicate any of these procedures are done so completely at your own risk. By reading the information on this site, you agree to assume complete responsibility for any and all actual or consequential damages that may arise from any information presented herein.