Here is what I heard of doing and then I tried it. It worked great! Boil a pot of water, pour it in a container that you will never use for food, put some dish powder soap (any kind) and drop your engine in it and let soak awhile. I did this twice and then dried it and ran some fuel through it to get the water out. After that I started the engine up and ran another tank of fuel in it. And would you believe that it actually seemed to run better than before? Oh, by the way, this engine was five years old with plenty of use on it. I don't think you would regret it if you tried it.

Sugarfoot