AiM MyChron3 Basic - Manual (Page 20)

20
Installing the Underspark thermocouple
When using a Cylinder Head Thermocouple ( CHT ) sensor, always remove the
spark plug washer before inserting the spark plug into the sensor.
When tightening and loosening the spark plug, minimise movement of the sensor
to avoid damage.
The following drawing shows the correct installation of the underspark
thermocouple.