If you are careful, you can pull off the head without messing up the gasket, it should be a rubber O ring type and if it stays in the channel, it will be ok. If it comes out, it takes an act of God to get that one to go back in. The head, if you are not sure, is just the top portion of the engine that the plug goes into. Not sure if I was clear or if you already knew that. Make sure your exhaust valve is working right while you're in there too. I doubt it would be a float problem, like Metal said, you'd have gas pouring out just sitting there. Clean out your power valve as well too, it may have gotten gunked up as well. wouldn't change your jetting as of yet, if nothing was done and it worked fine before, that ain't it.
If your carb is gummed up, you'd have ppower issues as well as it not even running right. Blow through your air passages and make sure they are clear too.
Keep us updated, good luck.