This instructible gives an easy fix for this problem which will make the carburetor operate as well (or at least close to as well) as it did when it was new and can be done in 30 minutes to an hour with the carb on the vehicle and with only minimal tools and a can of aerosol carburetor cleaner.
This process should work for about nine out of ten people with this problem, and if it doesn't work for you, it probably means that you need to do a complete carburetor rebuild.
Note: this is my first instuctable so give me some slack, and I will try to add more pictures/videos soon.
Step 1: Gather tools
1. Flat head screw driver
2. 3/16" wrench or driver
3. 1/4" wrench or ratchet
5. Carburetor cleaner (not shown; any brand from an auto part store should work)
6. Air compressor with 'blowgun" attachment. (not required but highly recommended)