Toro 74790 Operator's Manual page 36

Note:
Due to the deep recess around the spark
plug, blowing out the cavity with compressed air
is usually the most effective method for cleaning.
The spark plug is most accessible when the
blower housing is removed for cleaning.
Checking the Spark Plug
Important:
Do not clean the spark plug(s).
Always replace the spark plug(s) when it has: a
black coating, worn electrodes, an oily film, or
cracks.
If you see light brown or gray on the insulator, the
engine is operating properly. A black coating on the
insulator usually means the air cleaner is dirty.
Set the gap to 0.76 mm (0.030 inch).
Installing the Spark Plug
Tighten the spark plug(s) to 25 to 30 N∙m (18.5 to
22.1 ft-lb).
Figure 33
Figure 34
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Figure 35
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