I like the stebel, but it's not louder than the twin Hellas and theyve had inconsistent durability. Webbikeworld did a test and their tester failed and my stebil failed on my hyper...
This is true. I've fitted a Stebel Nautilus to my M696 and it worked fine for as long as I kept the bike. I've also fitted a Stebel Nautilus to my M1100 and it continues to work just fine too. But you're right, there are reports of inconsistent reliability.
If they stop working, then, maybe all they need is a bit of lube inside of the compressor.
The air horn on my daily driver (NA6 Miata) just stopped working today.
( this
http://www.amazon.com/Wolo-Model-417-Plastic-Trumpet/dp/B000BNH0I6/ref=pd_sbs_auto_36, and I've had it for about 5 years).
The compressor part is the same as Nautilus.
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Just unscrew the two philips. Easy.
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Inside looks OK.
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The magnet on one side is a bit broken, but no big deal.
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That's it. It works now.