4.24 Maintenance of spark plug
The state of the spark plug changes during operation as a consequence to the high mechanical,
chemical and thermal strain it is exposed to – it ages. Regular maintenance and check up´s of the
spark plug´s aging process is necessary in order to keep the engine reliable and safe.
For the beginning, it is important that the inner parts of the spark plug are clean. To maintain this,
the spark plug should be removed every 600 miles and cleaned using a wire brush (Do not burn the
spark plug out and don´t use any so called „spark plug cleaners“!). Also important is the right
distance of the electrodes. Isolator spark plugs hav a distance of 0.6mm. Since this distance grows
due to electrode burn up, the outer electrode needs to be bent in until it´s back to it´s original
distance of 0.6mm. This can either be done by using the supplied sensing gauge (see image 61.) or
by simply stacking 3 postcards on top of eachother and using them to measure the distance. The
appearance of the spark plug´s inner parts, the so called „face“ concludes the burn-up of the engine
and so gives the opportunity, to detect disturbances in the engine´s combustion processs timely
and thus enables early troubleshooting (See section 4.241).
When reinstalling the spark plug, do not forget to also reinstall the spark plug gasket.
After about 6000 miles the spark plug has aged so far, that it can´t bear up against the thermal
forces within the cylinder. To prevent possible damages to the engine, the spark plug has to be
exchanged about every 6000 miles.
The right spark plug for the engine of the city scooter „SR59 Berlin“ must have a heat-count of 240.
Never should spark plugs be used, that have a lower heat-count, because it might cause severe
damage to the engine. Spark plugs with a higher heat-count are unnecessary and will cause
complications.
Image 60. Sparkplug maintenance
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