How to MTD – Yard Machines 21inch 3 in 1 Lawn Mower Spark Plug Replacement post will explain the steps by step process for your Lawn Mower spark plug replacement.
Replace the spark plug at the beginning of every season OR after 100 hours of operation, whichever comes first.
Do an inspection after 25 hours of operation.
If you are using LONG LIFE Spark Plugs do an inspection at the beginning of each season OR after 25 hours of operation, whichever comes first.
This machine cames equiped with an Engine 159cc OHV POWERMORE®.
You can watch the video below OR scroll down to see the step by step instructions.
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First select the new spark plug.
F5RTC (Torch) Plug Recommended.
• NGK – BPR5ES
• Champion – RN12YC
• E3 – E3.22 , E3.16
Personally I bought the E3.22 spark plug.
• USING AN INCORRECT SPARK PLUG can cause engine damage.
• DO NOT check for sparks with spark plug removed
• DO NOT crank engine with spark plug removed.
To ensure proper engine operation the spark plug must be free of deposits and properly gapped
Second we will have to prepare the tools needed.
Third … now we can start the SPARK PLUG REPLACEMENT job.
Be sure to have the engine cool at this point.
Disconnect the spark plug boot from the spark plug and place the boot away from spark head.
Using the Ratchet, Drive extension and 13/16 Spark Plug Socket remove the spark plug by turning counter-clockwise.
Inspect the spark plug seat and be sure the OLD washer is on the plug you just removed.
Measure the plug gap on the NEW SPARK PLUG. HAS TO BE 0.030″ (0.762mm). Correct as necessary by bending side electrode.
Add a drop of oil on the spark plug thread.
Insert the NEW SPARK PLUG to the socket.
Thread the spark plug in by hand to avoid cross-threading until stops turning.
Using the Ratchet, Drive extension and 13/16 Spark Plug Socket tighten the spark plug. Tighten 1/2 turn after the spark plug seats to compress the washer.
When reinstalling a used spark plug tighten 1/8 – 1/4 turn after the spark plug seats to compress the washer.
DO NOT OVER-TIGHT the spark plug because you CAN DAMAGE THE THREAD IN THE CYLINDER HEAD.
A LOOSE SPARK PLUG CAN OVERHEAT AND DAMAGE THE ENGINE.
Reconnect the spark plug boot to the spark plug. Be sure the boot snaps in place securely.
Move the Lawn Mower OUTSIDE OF CLOSED SPACES and start the engine. Run it for 1 minute. Check for an easy start and a smooth run.
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