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The Honda GX25 is a 25cc, four-stroke, single-cylinder, overhead camshaft engine that produces approximately 1-horsepower at 7000 revolutions per minute.

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Why does the oil turn black every use?

after running my brushcutter fo an hour it stops and the oil is black

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@mopriestley what do your plugs look like? The engine is a honda gx25? Have you checked the valve? Done a compression test or a leak down test? It does sound like you have a lot of soot buildup inside your engine. Mist likely lots on your combustion chamber, oil sump, valvetrain etc. of course you changed your oil filter frequent etc. what‘s of greater concern is that your engine actually stops. Time to go over this engine and possibly consider a partially teardown/rebuilt.

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Thanks for that. new spark plug and filter. We don't have equipment to do the tests though. it runs fine with new oil for about an hour then stops till oil changed again.


@mopriestley after that hour, does the plug have soot on it? the engine is a GX25?


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MO PRIESTLEY will be eternally grateful.
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