Don't dismantle the actual valve, just take off car and then use a small screwdriver to push centre plunger down GENTLY, as it is this bit that sticks, and then you can really spray where it matters.
USE proper carb cleaner though and spray with silicone spray afterwards as this helps to resist build up of crap again.
I use DASH DANDY to spray after cleaning as it has a lot of silicone in it.
tabetha