CORRECT INSTALLATION OF SPARK PLUGS

Selecting the correct spark plug is essential for any engine to perform at its best

After selecting the correct plug, it is equally important to install it correctly. Here is a step by step instruction on how to replace old plugs with new ones, from NGK.
A torque wrench is required for the correct installation of a spark plug, even for a professional technician the estimation of the tightening torque is virtually impossible, says NGK.

NGK warns most spark plug failures can be traced back to an incorrect tightening torque.
If it is set too low, there is a risk of compression loss and plug overheating. It is also possible that the insulator or centre electrode may be damaged as a result of excess vibration.
If the tightening torque is set too high, the spark plug’s metal shell will be overstressed and possibly yield. The shell can also expand or distort.
The distortion causes the heat dissipation zones to be disrupted; overheating and melting of the electrodes or even engine damage can occur. Overtightening can easily occur when installing small thread diameter plugs (10mm and 12mm) which are common in motorbikes.
The image shown here displays examples of plugs that have been broken by not holding the spark plug socket square during installation, explains NGK.
To correctly install new spark plugs, NGK says to follow these steps:
1. Loosen the old spark plug
2. Before withdrawing the spark plug, remove any debris or loose encrustations from the plug hole with compressed air.
3. Unscrew the old spark plug.
4. Check the condition of the thread in the cylinder head and remove any excessive deposits in the spark plug bore area.
5. Check the thread reach and electrode gap on each spark plug prior to installation. Ensure the electrode gap sizes are consistent to manufacturer’s recommendations.
6. Never use spark plugs that have fallen onto a hard surface after removal from packaging as the ceramic insulator may have suffered damage.
7. Tighten the spark plug by hand until it seats.
8. Set the torque wrench to the correct tightening torque.
9. Ensure the socket of the torque wrench is fully engaged and parallel to the nut of the spark plug without tilting and then tighten.

For sales and technical inquiries, please call NGK on 1300 55 40 59.