A part that can cause difficult problems to solve is surely the carburettor especially on tuned lambretta scooters.
The links here underneath can be very interesting for people who are looking to improve their knowledge on Lambretta carburettor functionality. Good for several hours reading pleasure.
The Italian manufacture site, gives a nice product overview in Italian and English.
Tip: have a look at the free manuals (valued @ 16 €) under the ‘Customer Area’ that gives a full colour functional description of the workings of a carburettor.
Eurocarb Ltd. the British importer website, interesting overview with exploded parts diagrams!