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HomeRepair HelpRepairSmall engine runs poorly Repair
Small engine runs poorly
When your small engine runs poorly, runs rough, surges, or sputters, start with the carburetor, the most common cause. Stale or ethanol-blended fuel left in the carburetor during storage can evaporate and leave a sticky residue that clogs the fuel passages, causing small engine carburetor problems and poor performance. Clean the carburetor with carburetor cleaner, then rebuild or replace it if cleaning does not restore smooth operation. A small engine carburetor repair kit can correct issues with internal gaskets and other worn components. Next, inspect the spark plug for a cracked insulator, burned electrode, heavy carbon buildup, or a weak spark. Test it with a spark plug tester and replace it if defective. A clogged fuel filter is another possible cause, especially when old fuel was left in the fuel tank. Drain stale fuel and replace the filter before testing the engine again. These checks apply whether the engine is surging, sputtering, hesitating, or losing power. Enter your model number to find the exact carburetor, repair kit, spark plug, fuel filter, or other replacement part for your specific engine.
01 - Carburetor
The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the engine for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to run roughly. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.
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02 - Carburetor Repair Kit
The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the engine for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the carburetor and cause the engine to run roughly. If the carburetor is clogged, try cleaning it with carburetor cleaner. If cleaning the carburetor isn’t effective, rebuild or replace the entire carburetor.
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03 - Spark Plug
Inspect the spark plug for signs of wear or damage. If the porcelain insulator is cracked, an electrode is burned away or damaged, or there is heavy carbon buildup at the electrode, replace the spark plug. To determine if the spark plug is defective, use a spark plug tester. You should see a strong spark between the tester’s terminals when the engine is cranking. If there is no spark, this indicates that the spark plug is defective and should be replaced.
Highly Likely
04 - Fuel Filter
The fuel filter might be clogged. A clogged fuel filter is most commonly caused by leaving fuel in the engine for a long period of time. Over time, some of the ingredients in the fuel may evaporate, leaving behind a thicker, stickier substance. This sticky fuel can clog up the fuel filter and cause the engine to run roughly. If old fuel was left in the engine, drain the old fuel from the fuel tank and replace the fuel filter.
Less Common
Frequently Asked Questions
Why is my small engine running rough, sputtering, or surging?
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Can old gas cause a small engine to run rough?
How do I find the correct carburetor, repair kit, spark plug, or fuel filter for my small engine?
What should I do if my small engine still runs poorly after cleaning the carburetor?