Idling and How To?

Could be a few things...
Clutch drag can often cause a motor to die or idle erratically. You need to do whatever you can to minimize cable drag. Route your cables with long sweeping curves rather than sharp bends, don't secure them down too tight with wire ties or whatever, shoot some light weight oil down the inside of the cable housing to lower the drag on the inner cable. You could also upgrade to a better cable that has a lining inside it which has much less drag (check a good bike shop for better cables). The same goes for the throttle cable, if there is drag the slide may not seat the same all the time. If your cables drag, when you turn the handle bars the clutch may drag more or less, the slide may open or close a bit, the combo of these two changes can have a big effect on the idle. You may also have air leaks somewhere that can effect the idle....