Generally you don't get that much dirt in the engine. DON"T turn it over. Take the back plate off, the carberator out, and the head off. Flush every thing with fuel, reassemble and press on. If you think the engine has more dirt in it than can be handled in this manner then you need to completely disassemble it and clean with soap and water, rinse in alcohol to remove all the water, oil and reassemble.

Denis