Lambretta Tuning by Dave Webster - lots of information about Lambretta Tuning from one of the UK's most successful scooter racers.
How do you make a street scooter a racing scooter? This book gives the answer. It includes crankshaft modifications, flywheel modifications and excitations, pistons, standard cylinders, standard cylinder heads, expansion chambers, carburetors, porting, Japanese piston conversions, and transmissions.