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HomeRepair HelpMTD RepairMTD Lawn mower runs rough Repair
MTD Lawn mower runs rough
If your MTD lawn mower runs rough, sputters, or surges after starting, the carburetor is the first place to look. On many MTD models, stale fuel leaves behind a sticky residue that clogs the carburetor and upsets the fuel-air mix, which can make the lawn mower run rough or the engine run unevenly. Start by cleaning the carburetor with carburetor cleaner. If that does not fix it, rebuild it with a carburetor repair kit or replace the carburetor. Next, check the spark plug for a cracked insulator, burned electrode, or heavy carbon buildup, and use a spark plug tester to confirm it produces a strong spark while the engine is cranking. A weak or failed plug can cause lawn mower sputtering and rough running. If the problem started after old fuel sat in the tank, inspect the fuel filter too, since a clogged filter can restrict fuel flow and make the mower engine surge. Enter your MTD model number on RepairClinic.com to find the exact carburetor, carburetor repair kit, spark plug, fuel filter, or other replacement part that fits your lawn mower.
01 - MTD Carburetor
The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the lawn mower 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 - MTD Carburetor Repair Kit
The carburetor might be clogged. A clogged carburetor is most commonly caused by leaving fuel in the lawn mower 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 - MTD 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 - MTD Fuel Filter
The fuel filter might be clogged. A clogged fuel filter is most commonly caused by leaving old fuel in the lawn mower. 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 lawn mower, drain the old fuel from the fuel tank and replace the fuel filter.
Less Common
Frequently Asked Questions
Why does my MTD lawn mower run rough after starting?
How do I fix an MTD lawn mower that runs rough or sputters?
Can old gas make my MTD mower engine surge or run unevenly?
My MTD lawn mower has spark but runs rough. What should I check next?
How do I find the right carburetor, carburetor repair kit, spark plug, or fuel filter for my MTD lawn mower?