How i clean my bubbler is like this. Pipe cleaners or cotton buds down the hole. swirl it round til they're nice and black and resiny. then take a kettle and pour boiling hot water down the hole or the stem, not the carb. shake it around in the sink and laods of crap should come out. hold the bubbler with a nut cracker wen it gets too hot. rinse and repeat. then put another pipe cleaner down it and its good as new. do it more often then not and its easier. don't let it build up.