Hmmm, you running a stock head? If so, the compression is just OK, shouldnt make it run like that though.
I'd say yeah, check the carbs, I let them soak in a big coffee can full of carb cleaner overnight. Also, the brass part that the needle goes through taps out through the top the carb. Tap it out, and clean out all the green gunk. Sounds like a carb/reed issue now.