My carbs have all been sticky and/or seem to operate with a mind of their own. I am currently on my fourth carb out of three Samurais.
The best working one was the one I removed, blasted with cleaner and WD-40, then compressed air. And after a year of running great, it's starting to stick again. Time to reclean.
There's a guy in a tiny carb shop at the end of a weird alley near me. He has a few reconditioned ones he sells for $300 with a core. They look brand new, if you want to go that route. He has them on Craigslist often.
-motofabio