How to Replace the Spark Plug on A Push Lawn Mower?

17 minutes read

Replacing the spark plug on a push lawn mower is a relatively simple task that can help improve engine performance and ensure proper ignition. Here's a step-by-step guide on how to replace the spark plug:

  1. Prepare: Ensure that the lawn mower is turned off and the engine is cool. Disconnect the spark plug wire to avoid accidental engine starts.
  2. Locate the spark plug: The spark plug is typically located on the side or top of the engine. Look for a rubber or metal boot attached to a metal rod, which connects to the spark plug.
  3. Remove the old spark plug: Using a spark plug socket or a wrench, carefully loosen the spark plug by turning it counterclockwise. Once loose, unscrew it by hand until it can be removed completely.
  4. Inspect the spark plug: Examine the condition of the old spark plug. If it appears dirty, worn out, or the electrode tip is damaged, it's a good idea to replace it.
  5. Check the spark plug gap: The spark plug gap refers to the space between the tip of the electrode and the ground electrode, which should conform to the manufacturer's specifications. Use a spark plug gap tool or feeler gauge to ensure the gap matches the recommended measurement.
  6. Apply anti-seize compound (optional): To prevent the spark plug from seizing, you can apply a small amount of anti-seize compound to the threads of the new spark plug. However, always refer to the manufacturer's instructions first.
  7. Install the new spark plug: Carefully insert the new spark plug into the socket or wrench and gently place it into the spark plug hole. Begin tightening it by hand to avoid cross-threading.
  8. Tighten the spark plug: Using the spark plug socket or wrench, tighten the spark plug clockwise until it is snug and properly seated. Avoid over-tightening, as this can cause damage.
  9. Reconnect the spark plug wire: Slide the rubber or metal boot of the spark plug wire onto the metal rod, ensuring a secure connection.
  10. Test the lawn mower: After replacing the spark plug, start the lawn mower and check for smooth engine operation. If everything is running correctly, you have successfully replaced the spark plug.


Remember, always consult your lawn mower's manual for specific instructions and guidelines, as the process may vary depending on your particular model.

Best Push Lawn Mowers of 2024

1
YARDMAX 21 in. 170cc 2-in-1 Gas Walk Behind Push Lawn Mower with High Rear Wheels

Rating is 5 out of 5

YARDMAX 21 in. 170cc 2-in-1 Gas Walk Behind Push Lawn Mower with High Rear Wheels

  • Single-lever deck adjustment for quickly setting your mow height
  • MAXFlow Deck Technology – volute spiral deck design for better airflow and mulching
  • Heavy-duty, 16-gauge stamped steel deck
  • Durable, one-piece seamless steel deck reduces vibration
  • Seven cutting heights from 1.25″ to 3.75″
  • Double-ball-bearing wheels for easy, smooth mowing with less pushing effort
  • Adjustable, durable 3-position handle height
  • Folds for space-saving storage
  • 7 in. front and 11 in. rear wheels for stability and control
2
PowerSmart Gas Lawn Mower 21 Inch 2-in-1 with 144CC 4-Stroke Engine, Push Mower Gas Powered DB2321CR

Rating is 4.9 out of 5

PowerSmart Gas Lawn Mower 21 Inch 2-in-1 with 144CC 4-Stroke Engine, Push Mower Gas Powered DB2321CR

  • 144CC OHV ENGINE: reliable engine, recoil starter for easy start, forced air cooling system continuously deliver unbeatable grass cutting effect.
  • 21 INCH CUTTING DECK: patented cutting system with 21 inch cutting deck, wider mowing path helps you trim sizable yard fast.
  • 2-IN-1 PUSH MOWER: side-discharge easily pass thick grasses for quickest mowing, mulching lawn mower minces grass into super-fine bits for recycle.
  • GRASS HEIGHT ADJUSTABLE: 6 positions for adjust cutting height from 1.5" to 3.9", suitable for all kinds of grasses.
3
BILT HARD Gas Lawn Mower 20 inch, 2 in 1 170cc 4-Stroke OHV Engine Cordless Lawnmower, 8 Adjustable Cutting Heights Push Mowers for Lawn, Yard and Garden

Rating is 4.8 out of 5

BILT HARD Gas Lawn Mower 20 inch, 2 in 1 170cc 4-Stroke OHV Engine Cordless Lawnmower, 8 Adjustable Cutting Heights Push Mowers for Lawn, Yard and Garden

  • Auto Choke Engine - 170cc 4-stroke OHV engine, 6.5 ft.lb torque, 20 inch cutting deck.
  • Cutting Height - 8-position single lever four-wheel synchronized height adjustment from 1.2" to 3.2".
  • Mowing Convenience - 7" rear/6“ front double ball-bearing wheels achieve smooth movement, comfortable foam-wrapped angled grip eliminates grasp fatigue.
  • Durable Cutting Deck: 20" cutting deck and specialized blade delivering a clean, even cut. Enjoy years of high efficient mowing with superior cutting quality
4
Greenworks 40V 16" Cordless (Push) Lawn Mower (75+ Compatible Tools), 4.0Ah Battery and Charger Included

Rating is 4.7 out of 5

Greenworks 40V 16" Cordless (Push) Lawn Mower (75+ Compatible Tools), 4.0Ah Battery and Charger Included

  • CORDLESS LAWN MOWER – Get more done, faster, with Greenworks electric lawn mowers. This 40v push lawn mower provides the power you need with up to 45 minutes of runtime on a fully charged 4.0Ah battery. The battery completely charges in 120 minutes.Brushless motor : No
  • LIGHTWEIGHT, EASY TO USE – A lightweight 16” cutting deck allows for easy maneuvering through small to medium yards (up to ½ acre) more efficiently. Easy push button start and lighter weight make it a great choice for your lawn.
  • VERSATILE – Battery powered lawn mower has a single lever 5-position height adjustment with a cutting height range from 1-1/4" to 3-3/8" for the best cut in all environments. The 2-in-1 feature offers versatile use with mulching and rear bagging options.
  • MAINTENANCE FREE – This walk behind lawn mower is virtually maintenance free, with no gas, no oil and no emissions. It starts instantly and is quiet but delivers gas-like power for your toughest projects.
5
Yard Machines 11A-02BT729 20-in Push Lawn Mower with 125cc Briggs & Stratton Gas Powered Engine, Black and Red

Rating is 4.6 out of 5

Yard Machines 11A-02BT729 20-in Push Lawn Mower with 125cc Briggs & Stratton Gas Powered Engine, Black and Red

  • A 125cc OHV Briggs & Stratton engine delivers reliable power to quickly tackle your yard
  • Push mower ideal for small yards with minimal obstacles
  • 20-in. deck with side discharge to efficiantly spread grass clippings
  • 7-in wheels provide reliable traction to navigate your yard
  • Choose from 3 cutting heights
6
BLACK+DECKER Electric Lawn Mower, 10-Amp, Corded (BEMW472BH)

Rating is 4.5 out of 5

BLACK+DECKER Electric Lawn Mower, 10-Amp, Corded (BEMW472BH)

  • Lightweight corded electric mower gasless 10 Amp 15 inch electric mower for powering through rough grass.Ideal for 1/8 acre.Voltage : 120 V. Product Application : Cleaning.
  • Comfort grip bike handlebar design reduces friction and enhances maneuverability for small lawns
  • Enhanced clipping collection winged blade yields 30% better clipping collection
  • Push button start no-hassle startup easy-to- use features
  • Adjustable cutting height 6 adjustable cutting heights ranging from 1 inch to 3 inch
7
CRAFTSMAN Gas Powered Lawn Mower, 21-inch Push Mower, 140cc (M105)

Rating is 4.4 out of 5

CRAFTSMAN Gas Powered Lawn Mower, 21-inch Push Mower, 140cc (M105)

  • POWERFUL ENGINE: 140cc BRIGGS & STRATTON engine with auto-choke
  • MOWING CONVENIENCE: 21 in., 3-in-1 convertible deck lets you side discharge, mulch, or rear bag grass clippings
  • CLIPPING COLLECTION: Rear bag collects grass clippings for easy cleanup or composting
  • HEIGHT ADJUSTMENT: Dual-lever, 6-position height adjustment makes it easy to change cutting heights from 1.25 in. to 3.75 in. high
  • COMFORT: Adjustable loop handle for comfort while mowing. MULCH KIT: Included to help put nutrients back into soil for a healthy lawn
8
BLACK+DECKER 3-in-1 String Trimmer/Edger & Lawn Mower, 6.5-Amp, 12-Inch, Corded (MTE912) (Power cord not included), Black/Red

Rating is 4.3 out of 5

BLACK+DECKER 3-in-1 String Trimmer/Edger & Lawn Mower, 6.5-Amp, 12-Inch, Corded (MTE912) (Power cord not included), Black/Red

  • 3N1 DESIGN – Electric mower easily converts to string trimmer and edger via a built-in foot pedal for versatile use.
  • 6.5 AMP MOTOR – Supplies the ideal amount of power when trimming grass, weeds, and overgrowth.
  • GEAR DRIVE TRANSMISSION – For tackling tougher, thicker grass without getting bogged down.
  • AFS AUTOMATIC FEED SPOOL – Continuously feeds trimmer line without bumping for seamless, uninterrupted trimming.
  • ADJUSTABLE MOWER DECK AND TRIMMER HANDLE – Lawn mower deck and string trimmer handle are adjustable for ideal grass- cutting height and added comfort.
  • CORDED – Corded design offers unlimited runtime for even the biggest jobs.
  • INCLUDES – (1)GH912 trimmer/edger, (1) MTD100 detachable mower deck, (1) AF-100 spool, (1) auxiliary handle, (1) guard.
  • Note: Item requires power cord. Power cord not included


What is the impact of an improperly tightened spark plug on a push lawn mower's engine?

An improperly tightened spark plug on a push lawn mower's engine can have several impacts:

  1. Loss of compression: The spark plug is responsible for creating the spark that ignites the fuel-air mixture in the combustion chamber. If the spark plug is not properly tightened, it can lead to leakage of compressed air and fuel mixture, resulting in a loss of compression. This loss of compression can lead to poor engine performance and difficulties in starting the mower.
  2. Misfiring: An improperly tightened spark plug can cause the spark plug to move slightly, leading to a gap between the spark plug electrode and the engine cylinder. This can result in an erratic spark or misfiring. Misfiring can cause a decrease in power, rough idling, and poor acceleration of the lawn mower.
  3. Overheating: The spark plug plays a crucial role in dissipating heat from the engine. If the spark plug is not adequately tightened, it may not be able to transfer heat efficiently. This can cause the spark plug and the engine to overheat, leading to potential damage to the spark plug, engine components, or even engine seizure.
  4. Fuel Consumption and Emissions: An improperly tightened spark plug can disrupt the combustion process, leading to incomplete combustion of fuel. This can result in increased fuel consumption, reduced fuel efficiency, and higher emissions of pollutants like carbon monoxide (CO) and hydrocarbons (HC).
  5. Damage to the spark plug: In extreme cases, if the spark plug is too loose, it can get dislodged from the cylinder head completely. This can cause severe damage to the spark plug threads, cylinder head threads, and potentially even the engine itself, leading to costly repairs.


In summary, an improperly tightened spark plug can cause loss of compression, misfiring, overheating, increased fuel consumption, higher emissions, and potentially damage to the spark plug and engine components. Therefore, it is essential to properly tighten spark plugs to maintain the efficient operation and longevity of a push lawn mower's engine.


What is the purpose of an electrode in a spark plug for a push lawn mower?

The purpose of an electrode in a spark plug for a push lawn mower is to create an electric spark within the combustion chamber of the mower's engine. This spark ignites the air-fuel mixture, initiating the combustion process that powers the engine. The electrode is designed to withstand high temperatures and facilitate the smooth flow of electricity to generate a reliable spark.


How to test the ignition coil connected to a spark plug on a push lawn mower?

To test the ignition coil connected to a spark plug on a push lawn mower, you can follow the steps below:

  1. Make sure the engine is turned off and is cool. Remove the spark plug wire from the spark plug to disconnect it from the ignition coil.
  2. Use a spark plug socket and wrench to remove the spark plug from the cylinder head.
  3. Carefully reattach the spark plug wire to the spark plug but keep a safe distance from the spark plug hole.
  4. Ground the spark plug by placing its threaded end against a metal surface of the engine.
  5. Put on safety gloves and goggles to protect yourself. Have someone pull the starter cord to crank the engine while you observe the spark plug tip.
  6. Look for a visible spark at the tip of the spark plug. A healthy ignition coil should produce a strong, blue spark.
  7. If there is no spark or if the spark is weak and inconsistent, it indicates that the ignition coil is faulty and needs to be replaced. If a strong and consistent spark is present, the ignition coil is functioning properly.
  8. Reinstall the spark plug back into the cylinder head, making sure it is tightened securely.


Please note that if you are uncertain or uncomfortable with performing this test, it is recommended to consult a professional mechanic or small engine technician to troubleshoot and repair any ignition coil issues.


What is the role of an anti-seize compound when installing a spark plug on a push lawn mower?

The role of an anti-seize compound when installing a spark plug on a push lawn mower is to prevent the spark plug from seizing or getting stuck in the mower's engine over time.


A push lawn mower is typically used in outdoor environments where it can be exposed to various weather conditions, temperature fluctuations, and moisture. These conditions can cause rust, corrosion, and generally make the spark plugs difficult to remove in the future.


The anti-seize compound acts as a lubricant and a barrier between the spark plug and the mating surfaces of the engine. It helps to reduce friction, prevent rust or corrosion build-up, and make future spark plug removal easier. Additionally, the compound can assist in maintaining the integrity of the spark plug threads, ensuring a proper seal between the plug and the engine.


By applying a small amount of anti-seize compound to the threads of the spark plug before installation, one can help prolong the lifespan of the spark plug and prevent potential damage to the engine during future maintenance or removal.

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