Hyundai 1 inch Owner's Manual page 30

Using the wrong type of spark plug can result in engine damage.
1. Remove the spark plug cap and remove any dirt from around the spark
plug base.
2. Use the plug wrench to remove the spark plug.
3. Measure the plug gap with a feeler gauge. If the electrode or insulator is
damaged, replace the spark plug. Correct as necessary by carefully
bending the side electrode. The gap should be between 0.7mm and
0.8mm.
4. Check if the spark plug sealing washer is in good condition. In order to
avoid damage to the thread in the cylinder head , screw the spark plug in
carefully by hand.
5. Once the spark plug has touched the washer, screw it down with a spark
plug wrench and compress the washer. If a new spark plug is used,
tighten the plug another half turn to compress the sealing washer. If
replacing the used spark plug only tighten a 1/8 to a 1/4 turn more. The
spark plug needs to be fitted firmly but not over-tightened.
6. Refit the spark plug cap.
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