Modern Vespa

Howdy. all/ I have a 2004 GT 200 that was in storage for about 6 months. I unhooked the battery and put fuel stabilizer in the tank, but the storage place emptied the tank (they said for insurance reasons) so my fuel stabilizer was gone. Anyway, it starts right up, and idles strongly, but after about 30 seconds the idle gets slower and it finally dies. If you tweak the throttle just a hair to keep the idle up, it dies right away.
Trying to restart, it won't even idle.
I've tried turning the idle screw (in both direction) but that doesn't help.
Any thoughts on what the problem might be?
Thanks much.

It sounds as if you start the engine with the fuel tank empty or the fuel line clogged.
There is some fuel in the system and that is why the engine starts perfectly but there is no new fuel coming and therefore it dies.
Your engine is OK I'm sure, so no need to turn any screws.

It is a 2004 GT 200, is it carburetor or injection?

When did the storage place empty the tank?

Sounds like a clogged jet. When you open the throttle more air enters the system and more fuel has to come with it. If the jets in the carb are clogged, the extra fuel can't be added. This will cause the engine to stall. I've also seen one case where the idle would slow down as the engine warmed up due to too much fuel. But in that case I was also seeing black smoke out the tail pipe.

I'd probably start with a tear down and cleaning of the carburetor.

-Craig

It's fuel injection.
Storage place emptied the tank just a few days after I put it in storage. They said they would add a bit of oil to the fuel tank to keep moisture at bay, but not sure they actually did that.
To add some context, it was an Allied Van Lines moving and storage facility. They only informed me the tank had to be emptied after the movers had loaded the vespa into the moving truck. Grrrrr.

not if it's a GT200

I'll bet you dollars to donuts you need a carb clean a fuel system flush.

My 2005 GT 200 is carbureted, so your 2004 has to be as well.

When you added fuel stabilizer, did you then run the engine for a bit to push the treated fuel through the lines or did you add it after the bike was "parked"?

I agree with you. I expect that is what is needed. A cleaning and from the fuel tank onwards.