I want a louder horn
That little "beep, beep" of the OEM horn, IF heard by anyone, only makes them look around for a clown car. Since you're not in a clown car, and you want people to acknowledge your presence, a better horn is in order.
Get the low-tone; The 125 dB AM80 is popular, as is the 132 dB Freeway Blaster. They're way louder, and are a bolt-in replacement for the stock horn. Point the bell of the trumpet down so it doesn't collect water, and cover your ears before you test it in an enclosed space. Even with it pointing down, it is loud and can be heard by cars and other motorcycles easily.
If you look at the catalog you might be overwhelmed by the amount of choices FIAMM offers. So don't look at the catalog. It's generally the same product in different packaging to meet the needs of the retailer. Here are your criteria:
The low-tone horn is still relatively high-toned. It cuts through noise quite well. The difference is that when people hear a deep horn, they get more of that instinctive "Oh crap, what's going to smoosh me?" feeling. You want them to have the feeling that they're impinging on your space. It seems to produce a more pronounced effect than the high-tone horn. When you hear that low-tone horn, you look around for the big Cadillac that's about to turn your car into junkyard art.
It's a direct replacement. No relay is necessary, but it is recommended (see below). It includes a bracket for mounting. You can either remove the nut holding the horn to the bracket and retain the stock bracket, or remove the one bolt holding the bracket to the bike and use the new bracket instead. Just try and see; the brackets are very similar. Installation time is estimated at "120 seconds".
Notes on the horn
The top picture shows the stock horn on a naked bike. The bottom picture shows the new horn installed on a bike with a fairing.
The installation is very straightforward:
Remove the OEM horn by removing the two power connectors from the horn, then removing the nut at the top of the horn bracket.
OEM horn removed:
Here's a picture of the top of the replacement horn, a Fiamm Freeway Blaster, and one of the underside:
To install the new horn, start off by loose fitting it, with the wiring reattached, so you can figure out the best angle. Make sure that the mouth of the horn is pointing downwards, so as not to collect water, and that the existing wiring is not stretched. Most aftermarket horns will say something to the effect that they are "polarity-free", meaning that it doesn't matter which of the two horn wires you hook to which terminal. Check the instructions for your particular model.
Secure the bolt to the bracket, then tighten the bracket to the bike.
Here's how it looks after installation:
Using a relay to power your horn
To provide the most power, and thus get the most noise, you can wire a relay to power your horn. This isn't necessary, but it is a good idea. The OEM harness runs the horn power through a mile of wiring and a dozen different connections until it gets to the horn switch. There are lots of places for voltage drop. With a relay, you use the OEM wiring to power the relay and then put in new wiring for the horn. The relay uses a small amount of power (the original switch circuit) to turn on and off a bigger amount of power (the new heavier wire) to the horn. This is true for bigger headlights or any other higher-current-draw accessories you want to add to your motorcycle.
Stuff you'll need
All the components for this project are available at Wal-Mart/Radio Shack/Autozone-ish stores. Take the fuse out of the holder and don't connect anything to the battery until everything is in place.
First, study the schematic. This may be all the directions some people need.
Next, wire up the relay. Do this before you install it, so you don't have to take stuff apart if it doesn't work.
How this works
The pair 85-86 are the trigger. When a circuit is made through this pair, via the horn switch, a switch on the pair 30-87 is toggled from open to closed. When this switch is closed, 30-87 are connected; this connects the battery to the new horn, and we get sound.
Using a Stebel air horn
This is not a complete how-to; rather, an informal guide, with diagrams, and pictures and comments from the owners.
There is a wiring kit available, if you want to go that route, but you should be OK without it. The hardest part is going to be finding a place to mount it.
Diagram: File:Stebel Horn Schematic.pdf
The Stebel Nautilus Compact is a 12VDC electro-pneumatic horn drawing 18amps. Finding an area to install the horn on the Ninja 250 is somewhat problematic. For this installation, I chose the area alongside the left-hand cylinder, underneath the cowling, as this allows the horn to be mounted out of sight, remain reasonably well protected from the weather, and allow the blast of sound to escape with minimal interference. I designed a simple bracket that attaches to the left-hand ignition coil mounting bolts. Here are some photos of the bracket and Stebel installed on the Ninja 250.
Electric power is supplied via a new circuit from the battery, with a 20amp fuse and 12VDC relay. the relay coil is triggered by the original horn switch and wiring harness. This is the same as for the replacement horns described above.
Bring on the Noise... 139dB worth please.
I installed the Stebel Nautilus Compact on the '08 250. I left the stock horn wired in place, and you can just blip the horn button and get the standard "meep, meep". Handy for beeping at pedestrians without giving them a heart attack. But if you lay on the button, the air compressor spools up and the full force of the horn comes out.
I decided the best mounting location was on the right side, hanging off the lower radiator mount.
This is from the top. You can see the L bracket I used. It came with another horn kit sometime in the past. You can make or find one yourself.
In the interest of running as little wiring as possible, I mounted the relay directly above the new horn, using a factory threaded, but unused, mounting point. I pulled the leads for the stock horn through the center hole and to the relay. Power runs along the factory wiring harness and directly to the battery (for now). I'm going to put in a fused aux. harness. Power and negative leads for both horns share connectors. You can see the ground in the picture.
Showing wires to the stock horn.
And again, new wires to stock horn.
Overview of the area... relay up top, horn down below. Wiring is loose, but tucked behind the right side coil.
Google video... Forgive the bad radio station in the background. We only have 2; country and one hit wonders