If your small engine won't start, there are a few things you can do to troubleshoot the problem. First, check the fuel level and make sure there is fresh gasoline in the tank. If the fuel is old or stale, it may need to be replaced. Next, check the air filter and spark plugs to make sure they are clean and in good condition. Finally, if the engine still won't start, you may need to take it to a certified repair shop for further diagnosis and repairs.