Have noticed on start up there is an off beat rattle or clank noise that eventually disappears after approx 3 mins, have spoken to the supplying dealer, who says it’s the decompression valve and they’ll remove it under warranty, apparently mine isn’t the first and it’s ok to ride with this ‘‘fault’’. Still love the bike !!!
Decompression valve? No idea what that might be or what it is supposed to do.
At the same time I am reminded of many big Kawasakis I have owned that on start up could sound like the proverbial ‘bag of nails’ for a couple of minutes until starting to warm up. I got used to ignoring it. Just the way they were and not a single one of those engines ever gave me any kind of bother and the same lumps were easily happy to break 100k miles.
Just valve train noise at cold. I wouldn’t worry about it. My last ZX14 valve check at 25k found all within spec.
The V100’s engine is the only Guzzi engine i’m aware of that features an automatic decompression system. Probably necessitated by that 12.6 compression ratio and the big bore. To the uninitiated, a decompression system is a starting aid to make the starter and the
battery’s work easier. It achieves it’s goal via a small protrusion next to one of the exhaust camshaft lobes, that keeps an exhust valve slightly open during compression, so the piston has less pressure to work against. Once the engine starts counterweights are flung out and the protrusion moves out of the way.
This post was originally posted on Facebook by forum member noamlu *
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Wow - I’ve only ever seen this before on off-road 4-stroke singles. 
A video of a guy rebuilding one was showing how it works.
Ahh gotcha! Thanks. Yeah like Mike below says I recall that from big singles of old to allow the engine to turn over without resistance before kickstarting. Duh!
Not something I’d have thought desirable to do away with but what do I know?
I know on my own Mandello I have noticed some valvetrain clickety when cold but doesn’t bother me at all. Lot of busy work going on down there and I don’t have enough miles on yet to suspect any issue with gaps.
The designer must have thought that this was necessary to give the starter clutch, motor an easy time and probably a smaller battery could be used making the bike slightly lighter. Is it a wise move having it removed?
I’ve only seen it on diesel dump trucks and generators lol (although those had a manual lever not automatic)
I wonder is there a slight increase in valve wear due to this system
My Stelvio has just been in for this issue and the right hand decompression lever was removed by the dealer under instruction of the factory, which has resolved it. No issues with starting since.
Several others have reported similar on Facebook and the issue appears isolated to the right hand cylinder. The system is present on the exhaust cam on both sides and the majority of the parts appear identical, so an interesting one!
Apparently the factory have issued a technical bulletin instructing the removal of the right hand cylinder decompression lever on all E5+ V100 engines as a matter of course during servicing.
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Well, well! Who’d a thunk it? 
Reassuring it is supposedly OK to ride the bike/use it but one wonders what the potential downside of not removing it? Is it just noisy or about to lunch something?
Some of the old bikes had a decompression leaver which helped when using a kick start method. I always hold the clutch in when starting my California EV a slowly release it.
Hi all - I have my Stelvio at the dealer in Salt Lake City, but they are new to Guzzi and the U.S. Moto Guzzi tech reps don’t have the tech bulletin for removal of the decompression device. They are saying the left cylinder removal not the right where the noise is located. If anyone has a local dealer who have dealt with this properly could I get their name and number? Much appreciated.