Lots of good advice for you in these answers,skrez.

Can I just add that it is usually better [in my own experience] to set the idle screw on a four-stroke to allow a good transition from low revs to high as a target, rather than have any given rpm level in mind for the idle.

Once your transition is set, the resulting rpm is 'what you get with this particular engine at this particular stage in its life'. The idle rpm usually improves with time [i.e. becomes lower] as Saitos take quite a while to 'run in'. Periodic resetting of both upper and lower carb. needles is recommended during this time. Impatience can result in running too lean - sometimes with expensive results.

Once run in properly, you may find, also, that a fairly high level of nitro is needed to give the lowest idle prm for a given good transition.

I've also found that my four strokes [once they are run-in] seem to run better with fuel containing oil around the 15% level rather than the 18% to 20% some people use.

Good luck - the Saito 100 is a lovely engine!