Some say Seafoam in the fuel works good. On motorcycles I rev the engine to 2500 rpm and squirt distilled water directly into the carb throat or throttle body. Run maybe 12-16oz thru without letting the engine die. The water vapor will blast the carbon right off the pistons and out of the chamber. All kinds of nasty black [censored] comes out the exhaust if it's carboned up bad. Do this with the engine at full operating temperature. Injected engines don't carbon up nearly as bad as carbed motors.
From Genesis: "And God promised men that good and obedient wives would be found in all corners of the earth."
Then He made the earth round...and He laughed and laughed and laughed!