How to Change a Lawn Mower Spark Plug
Step 5: Install New Spark Plug
Install the new spark plug in the hole by hand, turning it to the right (clockwise). It should screw in easily. Don’t force the plug, since it can cause cross threading. Instead, unscrew the plug and try inserting it again.
Once the plug has been screwed in by hand, GENTLY tighten it with the wrench until snug. Don’t over tighten the spark plug, since it can cause the threads to strip or break the ceramic plug.