Did you search Amazon.com? I know they have 2 stroke books.
If you want a good tuning book and if you you are ICC or Rotax or just running a Dell’Orto carb then the Dell’Orto Primer from Green Flag Motorsports @ http://www.greenflag.net/ is a real good book.
Here are a couple URLs I found when I Googled “2 stroke engine theory:”
Basic 2 Cycle Theory –> http://www.oldengineshed.com/twocycthry.html
Two Stroke Technology
How two strokes really work.
by:The_Dave –> http://www.offroadhaven.com/porting%20a%202%20stroke%20engine/2%20stroke%20technology.htm
Bruce….