If you’ve never heard the Stebel Nautilus horn in person, it’s difficult to describe. “Loud” is insufficient. Sure it is loud – very loud at 148 db. The two-note tone created by the Nautilus could better be described as “piercing” or even “pseudo-deaffoning.” Both are great qualities in a scooter horn. If you’re looking for a great way to get that absent-minded cager’s attention, look no further. You’re likely to startle the cell phone right out of their hand.

Installing the Stebel Nautilus seems like a complex operation at first. It’s less complex the second time. But now that I’ve done three of these, I think I’ve got it figured out. If you try to look at all of it at once, it seems really daunting. If you break up the install into its basic tasks, it’s actually really easy, especially in the Blur.

There are two basic parts to getting the horn in:

1. Mounting the horn and the relay
2. Wiring the horn and the relay


  1. 6-8 ft of 14-guage red wire. 3 ft of 14-guage black wire
  2. One in-line fuse holder, also 14 guage, and some 20-amp fuses (I recommend the “blade” type automotive fuses)
  3. Four slide-type 14-guage crimp connectors (the kind that will fit the blade terminals on the horn and the relay)
  4. Two ring-type 14-guage crimp connectors (the kind that you can pass a bolt through)
  5. One 14-gauge junction connector (basically a tube for connecting two wires together)
  6. One 1/4″ diameter bolt, 1″ long, and a nut.


  1. Regular metric socket wrench set with 8mm-12mm sockets and extensions
  2. Medium size phillips (+) screwdriver
  3. Crimping tool (you can buy the crimping tool as part of a kit that will have all the connectors you need also)
  4. Drill with 1/4″ and 5/16″ drill bits
  5. Multi-meter (voltmeter you can use to test continuity)

Believe it or not, mounting one of these horns in a scooter is actually harder than doing the wiring work. It’s five times the size of the OEM horn, so cramming it into the space can be a bit sketchy depending on the scooter. In the Buddy, for example, it’s a total cram job. You’ve got to basically wedge it in there between the frame pieces and strap it down – and that’s after you’ve relocated some of the OEM electronic components. On the Blur, however, all we need to do is drill a hole in the OEM mount and we’re good to go. So let’s get started.

1. Disconnect the Battery.
Open your under-seat storage compartment. The battery is under a tabbed battery compartment cover just aft of the pet carrier bucket. Remove the compartment cover, then remove the two screws on either side of the battery cover itself. Now unscrew the negative (-) battery terminal and push the wire away from the post so that it can’t flop back and touch the terminal again.

2. Remove the horn cover
At the nose of the Blur, there is a black, triangular panel above the headlights and below the headset. It’s got the Genuine G logo in the center of it. That’s the horn cover. It’s attached from behind via two screws in the upper corners and then by a series of clip tabs around its perimeter. Remove the two screws, then gently pry up on those loose corners and work your way down to the big tab at the bottom point of the triangle. It’s pretty sturdy, so don’t worry too much about breaking it. You shouldn’t need anything but your fingers to get it loose.

3. Remove the OEM horn and bracket
With the horn cover removed, you should be able to see the black, circular, OEM horn. It’ll have two wires coming out of it, one green with a yellow stripe, the other black. Disconnect these and lay the wires aside. Be careful to pull on the connecters and not the wires – you don’t want to break these as you’ll need them later. Using a 12mm socket, remove the horn bracket (the horn will come with it). Save the bolt, as we’ll reuse this whole bracket assembly later on. Now grab an 8mm socket and remove the OEM horn from the bracket.

4. Mount the Nautilus and its relay on the OEM bracket.
We’re going to reuse the OEM bracket and OEM mounting point on the Blur’s frame to mount the new horn. We’re also going to use the bracket to mount the relay. Using a 5/16″ drill bit, drill a hole in the center of the OEM bracket (it’s best to start small and work your way up to 5/16″). We’re going to use the bolt/nut that came with the Nautilus to mount it to the bracket in this new hole, then use the original bolt and bracket hole to bolt the bracket back onto the bike. We’ll then use the 1/4″ hole on the end of the OEM bracket (where the old horn used to be mounted) as the mounting point for the relay. Use just a 1/4″ nut/bolt to secure the relay, but you’ll need to drill out the mounting hole on the tab to 1/4″ first. Get everything finger-tight for now. Test mount the new horn and relay and adjust your angles so that you’re not hitting anything. You can do all of this through the horn cover opening, there’s no need to remove the whole nose panel. Do a test fit, and then go ahead and pull the horn back out. We’ll get it all wired up, then mount it for good.

Stebel Nautilus Wiring DiagramWiring
This is actually easier than it seems at first. What you’re essentially doing is creating a new circuit off the (+) side of the battery, running it through the new horn via the relay, and then back to ground. You then use the OEM wires from the original horn to activate the relay. So if you think of this as two separate circuits, it helps keep things more simple. Also, if you have a multi-meter, it’s a very good idea to check the continuity of your wires as you make them, that way if something doesn’t work later in the process, you’ll know you at least have good wires.
1. Tying in to the battery for power
Using a ring connector and your in-line fuse holder, create a patch wire to attach to the (+) battery terminal. Then splice the other end of that fuse holder to a 6′ long piece of red 14-guage wire. You’re going to then feed that wire through the frame. Install a fuse and check for continuity. Then remove the fuse for now – we don’t want anything touching the frame and blowing your main fuse.

2. Feeding the wire through the frame
Since the battery negative (-) is grounded to the frame, we only need to run a positive (+) wire forward to the horn. The easiest way to do this is to remove the “seat bucket” – the pet carrier and actual seat. It’s held in using simply four 10mm bolts – two in the floor of the pet carrier and two in the rear by the battery. When lifting out the assembly, be sure to pause and disconnect the light on the right side. Now you should be able to feed the wire out of the battery box, down the right side of the bike frame and attach it with cable ties as you go. The tricky part will be getting the wire up through the front fork area and into the compartment where the horn is. A wire hanger will work well for this, as you can push it through, tie/tape/bend the electrical wire to it, and then pull it back through. Just be careful that you don’t snag other important wires along the way. Also be sure to turn the handle bars back and forth to make sure nothing is binding. It’s easy and appropriate to follow and even attach to the wiring bundle that already exists in this area. Secure everything, leaving some slack on both ends, and leaving at least 12-18″ of extra wire out the front of the bike.

3. Understanding the wiring
If you’ve never done anything like this before, the whole concept of the relay and the extra wiring probably seems really complex and daunting. Truth is, it’s a lot simpler than you think, it just isn’t explained very well anywhere that I’ve looked for guidance. Here’s how it works. We’re using a relay to capture the on/off signal from the OEM horn switch on your handlebars and use that to open/close a new circuit that we’ll create from the battery (the long red wire you just ran). You wouldn’t want to just plug the old wires into the new horn because the Nautilus draws a lot more power than the OEM horn and you’ll eventually burn out the switch. Instead we’re going to use the OEM horn switch to activate a new switch – the relay.

It’s easiest if you think of it as two separate circuits that intersect at the relay. You’ve got the new circuit you’ve created using new wire from the battery. That circuit runs from the battery, through the relay, into the new horn, and then back from the horn to the frame of the scooter (ground). The second circuit is the OEM horn circuit. The green/yellow (+) horn wire from the switch on the handle bar, and the black ground (-) wire. These plug into the relay and open/close the new circuit – sending electricity to the Nautilus and making a lot of noise!

4. Wiring the actual relay
There are a set of numbers stamped into the casing below each connector on the relay. You only need to remember one number: 85. The 85 connector blade is the lynch pin for this whole wiring job. At this point, you should have the relay mounted onto the OEM horn mounting bracket – turn it so that the connectors will face up once the bracket is installed for good. Remove the whole assembly from the scooter for now, but stay close to the bike as we’ll need to do one more dry fitting before we tighten everything down.

Take the green/yellow OEM horn wire and plug it into blade 85 on the relay. Now take the black OEM horn wire and plug it in opposite blade 85. You’re half way there.

Now you’re going to want to make a new red wire, about 12″ long, with a connector on each end, to run from the positive (+) blade terminal on the bottom of the new horn to the relay. Leave yourself some slack, but you don’t want a bunch of extra wire to manage either. Connect that wire from the positive (+) terminal on the horn to one of the open blades on the relay (at right angle to 85) – it doesn’t matter which one. So now you should have three of the four blade terminals on the relay connected to something – green/yellow on 85, black opposite, red at 90º on one side or the other.

Now it’s time to set the whole assembly in the scooter for just a second. You should have 12-18″ of red wire hanging out the front of the scooter (running from the back of the scooter). That wire is going to plug into the last open blade terminal on the relay. Make sure you’ve got enough slack to run that red wire to the relay with the horn in its final position, plus enough to lay the horn out of the compartment without disconnecting it. Cut the long red wire to length and crimp on a connector. Connect to the relay – you should only have one open slot left across from the red wire you just made. You should have all four terminals connected to something now. Two red wires opposite each other, and the OEM wires opposite each other.

Time to make one more wire. Create a black ground wire to run from the negative (-) terminal on the bottom of the horn to the frame of the scooter. Crimp a slide connector on one end (to connect to the blade terminal on the horn), and a ring terminal on the other end. The idea is to loosen some screw or bolt that fastens into the frame, then pass that screw or bolt through the ring terminal and bolt it back on to the frame. That’s your negative (-) return to ground, which connects you to the negative (-) battery terminal and completes our new horn circuit. On my bike, I grounded to the center mounting bolt for the nose body panel just above the horn compartment opening. I sandwiched the ring connecter between the bolt head and the washer so that it was metal to metal all the way to the frame beneath. Check your wire for continuity and connect the negative (-) terminal of the horn to frame ground. You now have a complete set of circuits.

5. The moment of truth
You’re going to need to do two things before you can test and see if your horn works.

A. Reconnect the negative (-) battery terminal in the battery compartment.
B. Install a 20 amp fuse in the in-line fuse holder you added to the positive (+) battery terminal

Now put your key in the ignition, switch it to “on”, and press the horn button. Hopefully you’ll hear the loud glory that is the Stebel Nautilus. If not, double check all your connections, double check continuity on your wires, make sure you’re grounded to the frame, and double check that you haven’t blown any fuses, and double-check the orientation of your relay wires relative to 85. I’ll add a trouble-shooting section at the end [of the final article, call me if you run into trouble].

6. Buttoning up
Presuming everything works and you’ve done a little victory dance to the music of your ringing ears, now it’s time to mount everything permanently and put the scooter back together. By now you’ve had the horn in and out a couple of times and can see the basic angle between the bracket and the horn to get the horn to hang properly without hitting any of the plastic. Go ahead and tighten up the nuts on the horn and the relay, then using the OEM bolt, re-mount the bracket and tighten down. Wiggle all your wires to make sure nothing is binding. Test the horn one more time to make sure it works, then reinstall the horn cover. Now put the seat bucket back in (don’t forget about the light) and re-install all the battery covers. Use some duct tape to tape a spare fuse inside the battery compartment. Test everything one last time, and fire up the bike for good measure.

Congratulations, you’re officially loud.

Nathaniel Salzman