Gasoline additive for carb messed up from sitting?

Is there such a thing as an additive that can be used in such a case? Last year I put my generator away without using the gasoline additive (Stabil) Now it runs crappy. It has always given me excellent service in the past. Can I run carb cleaner thru it? Injector cleaner? Is there something better?

My generator is a Honda EU3000is which is about 10 years old, but has very low hours on it. BTW, if you're in the market for a real nice generator, I endorse this one. Super quiet too. Plus it produces a modified sine wave, unlike the noisy construction type of generators that produce a square wave, "dirty" power, incapable of running sensitive electronic equipment.

Here is what they look like: