The bible of any two stroke engine tuner is Gordon Jennings Two Stroke Tuners Handbook.
This is problably the most comprehensive technical two stroke book written backed with test and experiments. It has a lot of information related to the entire two-stroke engine tuning including theory, examples, illustrations, data, formulas etc.
PDF copy available courtesy to edj.net/2stroke/jennings/
Also a good read is Two Stroke Performance Tuning by Graham Bell
Two-Stroke Performance TuningPDF copy available courtesy to:
http://iheartstella.com/resources/manuals/tuning/Graham-Bell-Two-Stroke-Performance-Tuning.pdf
And same books for amazon purchases:
Please can you help me with my Apache 50cc 2stroke quad have started to splutter and is loosing power???