I have oil and dirt all over the exterior of my lawnmower engine. How do I find the problem?

The exterior of the engine and the top of the mower deck are covered with oil/dirt. I assume I have an oil leak somewhere. How do I figure out where it's coming from? It's a Craftsman push lawn mower.I have oil and dirt all over the exterior of my lawnmower engine. How do I find the problem?
Clean it all up with solvent and a rag. After it is dry run it for a few minutes and the oil leak leak will be obvious. The dirt is what sticks to the oil. You likely have a Briggs and Stratton engine and since there are only few places that it will leak, you should have no trouble finding it. The o-ring on the bottom of the oil fill tube is probably the most common source of leakage on a vertical shaft Briggs.I have oil and dirt all over the exterior of my lawnmower engine. How do I find the problem?
You could try washing it up really well and then let it sit for awhile. You may be able to see where the oil is coming from.

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