the adjuster on my sirio feels pretty tight., hard to move with just fingers... do you have the black engine block or the silver one? i have the black and it is actually different than the silver block engine, my friend has the silver block engine and a few parts are different than my engine.
I have both. Apart from changing the material from steel to brass, the carbs on both generations of engine are identical. You'll notice that they've since gone to a cast aluminum carb instead of composite, and the single adjustment carb (their name for it) no longer has the removable spray bar - it's simply machined into the housing now.