This text includes recent developments in four-stroke technology. It outlines simple and inexpensive tuning modifications for road and occasional club competition engines, with an emphasis on economy and useable street power. This text also describes how modern engines can be modified for performance with cam, exhaust and carburation changes - and still pass emission inspections, and it explains how electronic controls and emission controls work. Graham Bell has also written ''Two-Stroke Performance Tuning'' and ''Four-Stroke Performance Tuning''.