Motorcyclists are invisible. That's the conclusion I've come to after years of riding. A cage/car driver can look you in the eyes and not see you. Somehow it just doesn't register to them that you're there, moving quickly and vulnerably exposed. I'm not one to rely on a horn or abuse a horn as so many drivers and riders do, but I am convinced that a loud horn, used at the appropriate moment can help prevent an accident or worse, serious injury. And I've not been at all happy with the stock horn on my last several motorcycles - the sound is like a timid "meep meep" or "Excuse me please, I'm here and smaller than you are". I much prefer a horn with a loud sound that sounds more like "Watch it buster!". Sounding like a Mac truck wouldn't be bad either. The Stebel Nautilus Compact air horn has been my solution. I've installed one on all my last few bikes and when I got my new 2013 F800GS adding a Stebel horn was one of my first priorities. I was afraid though that it wasn't going to be easy to find somewhere to put it. Here's the horn: On my BMW K1300GT I found a spot under the left fairing where the horn would fit as long as I did some minor surgery on the horn first. See that little protrusion at the bottom with the curve in it? I had to cut that right off with a hacksaw and then it fit. I held it in place using a couple of zip ties. My Triumph Tiger 800 was even more of a challenge. There was simply no room anywhere to place the entire horn so some pretty major surgery was required. With great care, I managed to separate the compressor part (that's the silver cylinder on the right side of the photo) from the horn part by cutting off those plastic arms holding the two parts together. Then I had to machine a piece of brass I had laying around in order to fit a silicon tube from the compressor to the horn. This was the biggest challenge and I dreaded having to do that again for the F800GS. On the Tiger I ended up putting the compressor way at the back of the bike, behind the pillion seat and under the tail piece luggage rack. I ran the silicon tubing all the way to the front of the bike to the horn part of the horn, which I attached with zip ties under the front fender where the original horn had been. The physical installation of the horn is a lot more challenging than the wiring part, and in spite of my fearing this would become a major project, I wanted that loud horn so badly that I rolled up my sleeves and started looking for a place it would fit on my GS. Luckily for me, the installation proved to be the easiest of all the horn installations I've done so far. And with this little guide, I hope to convince you to tackle the project yourself. Once I removed the left side panel (way easier than on my K1300GT) I found the stock horn was easily accessible and held in place with one bolt. I removed it and started the equivalent of a jigsaw puzzle by trying to place the Stebel horn in any orientation that would fit and still allow the side panel to be reinstalled. The optimum position for the horn is with the bugle part (where the sound comes out of) facing down so that water doesn't get in, and with the compressor vertical. After fooling around a bit, I noticed that with the horn in the optimal orientation, that little extruding part with the curve in it would fit perfectly over the top of the top-most of the two bolts (see photo). I couldn't actually bolt it in place, but a strong zip tie would work perfectly. I put the horn in position and tested to see if the side panel would still fit and with a happy cheer I found it did. Before putting on the zip ties to hold it in place, I turned to figuring out the wiring. Here you can see the area where I would install the horn (with the stock horn already removed) and you can see those two bolts I mentioned. The stock horn had been attached to the bottom one. Also note the original plug for the horn. Here's a better shot of the plug: If I can help it, I prefer not to cut any original connectors, just in case one day I would want to return the bike to original condition. I just had to find a plug that would fit this connector. A visit to my favourite BMW dealer's parts counter allowed me to find that BMW part # 833 004 023 44 was what I needed. Cost me all of twelve bucks: If you get this plug you'll notice that at the wire end in very small print each wire is numbered, #1 and #2. A multimeter quickly allowed me to determine that the #1 wire was the ground wire and #2 was the 12 volt positive supply. I hate crimp-type connectors and whenever I can I prefer to solder my connections and shrink wrap (or tape) them. Of course sometimes you need to be able to easily open and re-connect something so then you have little choice. In this case, I decided to solder my wires to the bottom of the horn compressor because I didn't want to risk eventual corrosion and also because the space at the bottom of the compressor was tight and quite close to the top of the radiator. By soldering my connections there, I was able to use less space than a connector would have taken, plus I was able to route the wire off to the side a little better and away from the heat of the radiator. Most packages of the Stebel Nautilus Compact air horn include a relay, and indeed one should be used on the power connection. The standard horn connection is unlikely to be able to supply the amperage that an air horn requires, so I was certainly going to use the relay. Another thing I do with all my bikes (because I'm a bit of a gadget nut) is to install a fuse panel and relay so that any devices I install wouldn't affect the CanBus system these bikes use. Having already installed my fuse panel (I got mine from Twisted Throttle and it's branded with their name but is really a FuzeBlock), I was going to use that to supply power to the horn. Since the FuzeBlock already has a relay, technically another relay for the horn wasn't needed, except for the fact that the horn needed to be triggered only when the standard horn button was pressed and not always on. So this is how I did my wiring: Original horn wire #1 (remember this was the ground wire) I attached to the Stebel relay's ground connection (labelled as #86). The connections on the bottom of the compressor were labelled as ground and 12v+ so I took a wire from the ground lug on the compressor and ran it to one of the ground terminals on my FuzeBlock. (I could have run a wire to a bolt on the frame or engine but I thought this would be a cleaner install.) The 12v+ connector on the compressor I connected to the #87 terminal on the relay. I took the #2 wire from the original horn connection (this was going to trigger the relay whenever the horn button was pressed) and connected to terminal #85 on the relay. The last relay terminal, #30 was for power and I connected it to a 12v+ terminal on my FuzeBlock. You would probably want to use crimp-on connectors at the relay to allow for easy disconnection if needed, and then individually wrap them carefully with tape or heat-shrink tubing to prevent them from touching anything else. Maybe overkill, but I like to be safe. Again since I hate crimp-ons, and since I have no problem cutting one of my wires and then reconnecting it if I ever have to, I soldered my connections here. In this photo you can see everything installed and ready for the side panel to be put back on. Note that I used another zip tie to attach the relay to a hole that was handy on the frame so didn't have to make a bracket or drill a new hole. Works like a charm, and I feel a bit safer by being able to alert car drivers that I'm there. Hope this is of help to you folks.