Been working on a small lawnmower engine. Put away working, it is now the middle of winter. Normally very easy to start, got it to run once a few days ago (very hard start) then never since. It will not even try, no chugging.

One of the few remaining mysteries, even when dry the spark plug hole expels black residue when the engine is cranked. Is this normal soot residue, or a concern?

I have replaced the gas and oil. The air filter is very clean.

1 Answer 1


Carbon buildup on top of the piston is not uncommon on these types of engines.

So what you are describing is typical.

  • Thank you. I can confirm that the soot was not the issue. A new sparkplug fixed the issue.
    – Jonathon
    Jan 14, 2021 at 15:10

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