You may have to remove the air filter housing to get access to the carb.
Just unscrew the bolt on the bottom of the carb. The float bowl can be pulled down and off. There should be a float on a pivot that goes up and down to close and open the needle valve to the carb. Pull the pin out of the pivot and the float will come off, and the needle will probably fall out and get lost if you're not careful. Get some cotton swabs and some carb cleaner and clean out the gunk in the needle valve seat. Clean off the needle valve and put it all back together.
If this doesn't work for you, just say so and I'm sure somebody will have a better answer to help out.