Stelvio 8V Groaning Sound in Fuel Tank When Parked After Ride

[Bonaventure]

Sounds like a fog horn waaaaay off in the distance and very faint, I guess it's the fuel pump pressure equalizing?  It has to do with the engine radiating heat up and around the tank and causing a temperature induced change in vapor pressure inside, is my guess.   It will sit and do this until it cools down.  Rate of about, I don't know, maybe 1 per minute.  Duration maybe 2 or 3 seconds.  Certainly adds some personality to the beast !!

[Lcarlson]

Mine does it too. Apparently very common for Guzzis.

[kingoffleece]

Tank pressure venting.

[AH Fan]

Yup .............. pressure relief.
All my 8Vs do it to a degree but not so for the others?

Ciao

[Rhodan]

My V7 does it too.

[Bulldog9]

It's the fuel evap system. There are several threads on how to eliminate the charcoal canister and check valve contraption. I removed mine on the Norge & Griso. Jury is out on any performance gains. I noticed an immediate change in a more stable idle, and maybe a small improvement in throttle response, but not much.  Of course now the fuel tank vents to atmosphere.

[JeffOlson]

^  I did the same with my Norge. No more groaning, at least not from the bike!

[ohiorider]

From a B1100 manual.  Examples of Euro vs USA tank venting.




Euro venting to atmosphere




USA venting thru carbon canister.

[Bonaventure]

As long as the canister system is working right, I'll probably keep it intact.   

[JeffOlson]

The charcoal canister on a former BMW 7 Series went bad from gas pump jockeys over-filling the tank. (In nanny-state Oregon, we are not allowed to fill our own automobile gas tanks.) It cost nearly $1,000 to replace it. Fortunately, Kuni BMW took care of it for me. Just a cautionary tale about charcoal canisters...