Modern Vespa

Hello all I was wondering if anyone had some advice. About a year and a half ago I replaced the fuel pump and fuel injector. It's been running well but it sat recently for a couple of months and I went out to start it But every time I try to give it some throttle it just stalls out. I tried adding fuel additive to the gas tank, then drained the gas tank and added new fuel, And replace the fuel injector. But still having the same symptoms. Thank you for any help
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Bad seat sensor? You have to be sitting on it for it to rev. If the seat sensor is bad, that might cause those symptoms.

Thank you for the suggestion. I think my seat sensor might be working intermittently because many times I've been standing on the side of it and have been able to rev it But since you suggested the seat sensor I sat on it and it revs just fine.
thank you You fixed my scooter.
And I can also stand on the side of it now and throttle it just fine... but maybe that's because of a faulty seat sensor regardless thank you very much!!

how old is the battery ? ever have it load tested? a cell going bad with cause this issue.

yeah the battery's a few years old. If it happens again I will look into that. Thank you for the tip!