On my Kawasaki Bayou 250 there's gas getting to my Air Filter...What?

[Taylor B]

I've been having terrible performance from my 2006 Kawasaki Bayou 250 ever since I bought it from someone about two months ago. I know it's not running in optimal condition because I have ridden a few of the same model quads before. Also when it revs up and back down into idle, it makes kind of a bogging down noise. I have checked the spark plugs and they were completely black, so I had adjusted that and it seemed to have worked a bit, as it wasn't black anymore afterwards. I haven't looked into the carb much, just mixed a little carb cleaner with the last few fill-ups. The oil is good. Then when I had checked the air filter, I could immediately smell gas, and there was splatter marks inside the air filter container. Is that normal? What do you think could be the main problem here? I could really use the help, so if you have any suggestions or reccomedations then I'd would really appreciate it