it sounds like your running way too rick but if tuning isnt the issue then i would tale the carb off and apart give it a good clean and see if that helps any
yeh seal it. also how old is it? mine had problems when the motor was stuffed. my crank was scratched real bad and the pinch on the piston and sleeve. well i could almost push the piston out the top it was that loose. new motor and wow. got some respect back for the little 3.3