B&S V-Twin carburetor repair

I have carburetor "issues" on my B&S V-Twin 12 HP generator engine. The engine has less than 20 hours on it... so I'm convinced it doesn't need a rebuild kit.
I'm sure that the gas in the tank had gotten very old, so I've tried cleaning the carburetor, but it still doesn't work.
There is a needle valve on the outside that is covered with a plastic cap that I can't remove. I think this is the culprit.
Does anyone know how to remove the plastic cover for this needle valve. The cover has a notch on it that limits it's movement.
Anyone who can help me with this is worth a gazillion bucks.
Thanks.... Greg
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