FAQ: Why does my GTS groan/moan/moo or fart when off?
This noise is nothing to worry about. It is simply the evap system equalising pressure between the fuel tank and the atmosphere via the carbon cannister. The evap system is meant primarily to meet CARB regulations but has been homologated for the whole of the USA. The system has been known to cause lots of problems with bad running and is often disabled or removed by the owners.

The European GTS does not make this noise, as it has no evap system. Removing the evap system will have a similar effect of stopping the noise.

Here is a picture of the evap system cannister which has been removed from a GTS

and some other links to the symptom.

My scooter "farts"
Why is my GT200 mooing? o_O
GTS Noise after running
My GTS was farting today...
Weird moaning sound coming from my Vespa?! (audio clip)

The article on how to disable the evap system:

EVAP Hose Removal
LX150 Complete EVAP System Removal
Evaporation System: canister replacement
MP3 250: Removal of the evap canister and roll over valve
Last Updated Mon, 23 Aug 2021 05:28:53 +0000

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