If your chainsaw isn't running well, a dirty carburetor could be the problem. You can take it apart, clean it and rebuild it, using a carburetor rebuild kit. This repair guide takes you through the process.
If the engine won't start even though there's fuel in the chainsaw, the carburetor could be the problem. Sometimes, it's easier to replace the carburetor than to clean it and rebuild it. Follow these steps to do the job yourself in about half an hour.