I figure they must have answered a handful of questions a bunch of times.
(and I usually find a thread of some sort in archive. (ie. search). If something doesn't make sense or You have an Idea to throw out there you can usually "draw them out"....Friar-Tuck
Nice Post Tuck...
The only things I have avoided were anything with friction modifiers....Friar-Tuck
Definately avoid FM's in 2S, for your clutch plates welfare.... they work great on 4Stroke applications for an isolated cam/valve train system (KTM, Honda, Etc...)
Unlike a 4S where the combustion process adds products of combustion to the oil, 2S oil actually only gets the wear particles from the gears and clutch plates. If you tend to lug in the woods, slip the clutch alot, or put alot of torque to the ground (drags, real MX, or dunes) you should change the oil after every outting.
Most riders can get away with a fairly inexpensive oil like ATF and change it after every outting for cheap. If you have alot of motor work into your bike and ride it hard... then generally the oil change is part of the prep for the next outting, just like the air filter change.
Like mentioned in other threads, I use H*nda HP Trans Oil SAE 80W/85W.
Search Engine will get you alot of answers, you can even Bump an old post for a refresher...
Sly