1) Before installation always make sure that you use the proper type of spark plug for a particular engine.

2) Check before installation whether the spark plug is provided with an external gasket. If it is, also check that the old external gasket did not stay in the cylinder head from the preceding spark plug. (this is not valid for taper seat spark plugs).

3) Tightening torque must be within tolerances given in the table above.

4) At spark plug installation and removal from cylinder head do not apply force on the insulator.

5) Always use the correct spark plug wrench with a centering ring made from soft material.

6) Tightening torque must be applied perpendicular to the spark plug axis.

7) Tightening torque can only be applied in cases where the wrench is fitted correctly across the entire length of the hexagon of the spark plug metal shell.

8) At installation, if the spark plug tightening torque is overrun by 50% or more, the spark plug must be discarded.

9) Spark plug installation and removal from the cylinder head must be carried out only when the engine is at ambient temperature. Removal and installation of spark plugs while hot can actually cause thread and cylinder head damage.

10) After spark plug installation check that the cable boots are properly fixed to the spark plugs.