Setting the Spark Plug Gaps on a Riding Mower

When replacing spark plugs, it is critical that the correct gap be set. The gap is the space between the hook and the center electrode on the bottom of the plug. Too much gap, and the riding mower will not run efficiently. Too narrow of a gap, and the spark will be too weak to start the riding mower. Setting the spark plug gaps on a riding mower, before installing the plugs, requires a gap tool. Gap tools are round discs with a graduating thickness or graduating wires around the circumference. Gap tools are available at auto parts stores.

Gap tool

Instructions

- 1
  Check the owner's manual for your riding mower for the correct spark plug gap. Most riding mowers require either a .030 or .040 gap. Some spark plug packages list the various brands on the back of the package, along with the correct gap.
- 2
  Find the correct gap size on your gap tool. The gap tool has the gap size stamped around the circumference of the disc. Slide the part of the gap tool with the correct gap size in between the center electrode and side electrode. The side electrode is the metal hook over the center electrode at the bottom of the plug.
- 3
  Bend the hook down or up with the small hook on the gap tool. There is a tab on the gap tool with two notches on each side. Fit the notch over the curve of the side electrode, and bend the electrode up or down as necessary.
- 4
  Check the gap space again with the gap tool. Continue making adjustments as necessary until you attain the proper gap.

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