Reading the Spark Plug
With any tuning you need to check that the air/fuel ratio is correct. Too lean and the engine will heat seize. The easiest way to check the correct air/fuel ratio is by checking the colour of the deposits on the spark plug a.k.a plug chopping.
Here is link to external Lambretta info for now.
http://www.lambretta.co.uk/downloads/sparkplug.html
Note: For Vespa Labs we want to do measurements with our Wideband Oxygen Sensor