Link provided by Weimiedog on Chainsaw Repair http://dirtrider.net/forums3/threads/cylinder-porting-basic-principles-by-eric-gorr.185105/ This is basic stuff about 2 stroke engines in general and is not specific to the dirtbike world. If you ever wondered what the builders do read this.
Good link, KRL. That Weimiedog is one of the more underrated chainsaw "geeks" (his words, not mine) around. Ever watch his videos on AM parts? His one on taking an AM saw out to test in the maple stand reminds me of most of my own cutting experiences.