What to do when you see your Itoh line trimmer leaking gas
Move the line trimmer to a well-ventilated area and check the fuel lines for cracks. Replace the fuel lines if they're leaking. If fuel leaks from the carburetor, rebuild or replace the carburetor to prevent gas from leaking.
Check the fuel tank cap and its seal. Replace the fuel tank cap if its seal is damaged and leaking.
Check the fuel tank and replace the tank if it's damaged.
How to troubleshoot your Itoh line trimmer when it runs rough
If the fuel has been in the tank unused for months, it can pick up moisture and fail to ignite (that's why you should drain the fuel before storing for the winter or add fuel stabilizer to the tank). Replace the fuel with fresh if it's old and untreated with stabilizer. You might also need to replace the fuel filter at the same time. Performing preventive maintenance including a line trimmer tune-up will also help the engine run smoothly.
Check the fuel lines for cracks and replace them if necessary. If you still have problems after checking those issues, consider replacing or rebuilding the carburetor.