Friday, May 31, 2013

Project report: Installing a Stebel Nautilus Compact air horn

The stock horn on the Vespa GTS 300 i.e. emits a very polite "meep" when you press the button. Press it twice, and you get "meep-meep".

Until our recent trip to Italy, I couldn't understand why you would ever want to go "meep-meep" when you're in heavy downtown traffic doing 60 km/h and the oblivious cabby next to you suddenly moves to obliterate you. It's even more of a mystery when you consider that the Vespa GTS can cruise all day long on the autoroute at 118 km/h.

Italy changed my opinion of the engineers at Piaggio.

In Italy, the stock horn fits right in. In Italy you use the horn politely on blind corners; or just before cutting another vehicle off with brio; or when you coast down a street in Sorrento (here we call them sidewalks) and want to announce your arrival politely to your friends seated at tables in the street enjoying pizza and drinking Chianti; or when you want to join ten or fifteen other drivers who are honking to 'help' clear congested traffic. Those uses account for 99.99% of all Italian horn use. And "meep-meep" or sometimes "meeeeeeeeeeeeep!!!", is just the right tone. You see, in Italy the people in the cars KNOW they are sharing the road with motorbikes, and expect to be cut off with brio.

That won't do here. Here when you need your horn, you have to get the attention of Cadillac Escalades in the hands of well-meaning, well-heeled, but distracted, assassins. You want to press the button and go "BBBLLLLAAAAAAAAAAAAAH!".

Fortunately the Italians invented just the thing for North American needs. It's name is the Stebel Compact Nautilus, and it's an air horn for motorbikes. It goes "BBBLLLLAAAAAAAAAAAAAH!".

The trick nowadays is finding one of these gems. The manufacturer seems to have discontinued them (likely too little demand in Italy; too few buyers here). Fortunately I have one.

I extracted it from my Vespa LX 150 and here's how you install it in a Vespa GTS.

This is not especially difficult.

First find a Stebel Compact Nautilus on Ebay and snatch it up.

Once you have it, the bit that's tricky, is getting the right kind of juice to the horn.

The stock horn gets all the power it needs straight from the horn button. The Stebel horn is a serious horn. It needs power straight from the battery. When in operation it draws close to 20 amps. It needs its own fuse (I use a 25A fuse).

Here's wiring diagram that I made for the installation. If you click on it you'll get a larger more user-friendly image.

The first thing you need to do to get the installation going is to open up the bike.

First remove the Piaggio badge.
Next remove the single screw that secures the horncast.

Slide the horncast up, and off the bike. Next remove the two kneepad panels.

That exposes the screws retaining the legshield and glove box. There are two screws under the horncast, two screws at the base of each side of the legshield on the rider's side side, two screws behind each of the kneepads. Finally, there is another screw inside the glovebox. Once all the screws are removed, and once you remove the cap from the radiator fill tube,  it's possible to wiggle the legshield free. Here's a link to an excellent video produced by Mic Bergsma that will make this all crystal clear.
Now disconnect and remove the stock Vespa horn. The wires that are connected to the stock horn are then reconnected to the 85 and 86 terminals of the automotive relay. The automotive relay can be zip tied to the horn assembly.

Now run the negative lead from the terminal strip to the negative Stebel horn terminal located on the base of the horn. Run the positive 25A fused lead from the terminal strip to the 30 terminal of the relay. Now run a positive lead from the 87 terminal of the relay to the positive terminal of the Stebel horn.

Here's video that shows what the terminal strip I made looks like. It's handy because it makes it easy to install more circuits (like heated grips, eventually).

Working from the rider side of the legshield, wiggle the horn into position so that the horn is essentially vertical with the mouth of the trumpet aligned with the horncast opening. The fit is extremely snug. I was not able to use a zip tie on it. Once the legshield is buttoned back up, the horn will be stuck there and will not move.

Here are some photos showing the horn installed and that relay zip tied in place.
Before buttoning the Vespa back up, it's best to test the installation to make sure that the horn is working well. Here's a video that follows the negative and positive electrical leads from the battery, up through the interior of the legshield, over to the terminal strip, and then shows that horn test.

Now that the horn has passed its test, and the ringing is subsiding in your ear, it's time to put the bike back together.

There's a trick. You knew that there had to be a trick, right?

It took me some cursing and Googling, and I'll spare you the pain.

Piaggio has a fiendish streak in their industrial design, usually involving things that lock, like the glovebox, for instance.

It turns out that wiggling the glovebox into place and making sure that the mechanical link that unlocks the glovebox when you push on the ignition switch assembly, is impossible, unless you get an elastic band, hook it on the base of the dogleg lever that actuates the glovebox lock release, pass the elastic to the front of the legshield and hook it onto something (anything will do), all to make sure that the blasted little free-floating, four-flushing, dog-leg lever stays put in the retracted position.

Now you can go ahead and wiggle the legshield back into position, and button everything back up.

Simple (OK I cursed a little). But now I have my loud horn back. Yesssssss! Feeling safer already, and it's already saved my bacon on a couple of occasions.


SonjaM said...

Well done, you become quite the expert. We had a Wolo Bad Boy installed since we couldn't get our hands on a Stebel but it did the trick just the same.

The noise level however, is likely not legal in Germany, and we will have to convert back Bella back to "meep meep". When we asked other scooterists what horn they use the answer was: the standard horn, what else. When most people hear that specific sound they seem to know a scooter wants through ;-)

But the crowd of SUV drivers (female, 20 to 40, regular cellphone user) is growing, so maybe there will be a future for 'BRAAAAAP"

Canajun said...

I had a set of air horns on a previous bike and I'd sometimes forget I had them. When I hit the horn button I'd scare myself!

Anonymous said...

Ha, you really built suspense in that video! That is pretty loud!!! It's fantastic that you're so handy; I wish I could say the same for myself (or loved one who could help me).

I wonder whether this would work for a (cough) Honda Giorno? :-) Thanks for sharing! Also appreciated your premium gas investigation. And other stuff too!

David Masse said...

Sonja, it's interesting how different North Americans and Europeans are, and horns and the way they are used really stands out as a good example.

A guy I know found a way to keep the stock horn on his GTS and add the Stebel by using an add-on button for the Stebel. Quite ingenious really.

David Masse said...

Funny Dave, I can just picture that.

David Masse said...

Danielle, the Giorno seems similar to the Metropolitan. It should accomodate a larger horn too.

I'm always pleased when my blog helps someone who is just beginning to consider commuting on a motorbike.

Thanks for the kind words.

The copyright in all text and photographs, except as noted, belongs to David Masse.