Yes, there are. But that's not easily explained. It's like rocket science :P
Try reading some books on 2-stroke tuning, like "Two-stroke Performance Tuning" by Alexander Graham Bell or Gordon Jennings two-stroke tuning book.
If you feel bold, try "Design and Simulation of Two Stroke Engines" by Gordon Blair. That one's real mathematical and for the hardcore tuner, not something to begin with.