Over the years a lot of us have found Marvel Mystery Oil to work great. It will also free up a gummed engine. Marvel Mystery Oil was developed in 1926 for the use in air craft engines. It works for oil treatment as well as gas treatment and it cost less than $5 a quart.

I put it in my lawn mower gas, my truck, and my O.S. engines. All you need is a few drop down the carb of your engine, and spin it over a few times.

You can get it at any Orielly's, Auto Zone, Napa, or any other automotive supply store.

Frank