If you want the engine to look like new, use the crockpot method with an old crockpot YOU WILL NEVER USE FOR FOOD AGAIN.

Disassemble the engine as far as you are able (at a minimum, remove the carb, glo plug and backplate and associated gaskets ).

Put in a crockpot.

Cover with permanent type antifreeze (I use the green stuff - Prestone ?? )

Make sure the crockpot is outside, then turn the crockpot on low and leave on overnite.

Remove the engine/parts the next day and thoroughly wash AND RINSE with dish soap and water.

Put the parts in a 200 degree oven for about 30 minutes.

When the parts are cool, lubericate with afterrun oil (or airtool oil ) and reassemble.

The engine will come out looking like new.