Tuning Vespas the Norrie Kerr Way 1988:

This is a very interesting book although some of the items such as exhaust power valves are a little outdated. It covers tools, bottom end tuning and port timing, very basic port work for a Malossi 210 kit, small frame barrel conversions, cylinder heads, gearing, carburation, expansion chambers, basic brakes (no disk brakes), reed valves, ignition, and power valves. It also contains formulas for different tuning applications and pictures of how to modify stock casings to accept reed valves and large barrel kits.

Lambretta Performance Tuning and Conversions:

This covers conversions from one smaller cc motor to a larger production model engine (ex. LI 125 to Li 150 spec), other standard barrel conversions, defines stage 1 tuning on most models, carburetors, exhaust systems, port timing, gearing, disk brakes, and has a handy gear chart in the back. It is a reproduction of an original book from the 60's so it basically deals with modifying original Lambretta barrels and does not cover any of the more modern tuning tricks like expansion chambers, barrel kits, new carbs, electronic igntion, hydraulics, etc..

Lambretta Tuning Manual:

This covers how to convert a road going bike into a race bike. It includes crankshaft modifications, flywheel modifications and igntion, pistons, standard barrels, standard cylinder heads, expansion chambers, carburation, porting, Japanese piston conversions and gearing.

Two Stroke Performance Tuning

Although this book is directed to small bikes and karts all the information is relevant to two stroke scooters. Excellent reference material to make your bike faster. It covers cylinder heads, porting, exhaust design, carburation, ignition, lubrication, and gearing.