as far as i know type f is correct. that's what i put in my sachs tranny, as was recomended to me.
gap should be .18 to .20 most gapping gauges don't go down past .20, but you can eyeball it pretty good from there.
as far as premix goes, yeah, my sachs mopet says "50:1" on it so that's what goes in it. my motron says "40:1" so that's going to be the ratio for it as well.... each moped is different! and everyone has different opinions about premix..... but generally the more oil you put in the mix, the richer it will run, and will leave carbon buildup everywhere, but will also protect the engine from going lean and seizeing and other not fun stuff.
_If anyone hates on you for asking basic questions like that they are just haters so just shake them off. Everyone has to start somewhere and its better to ask questions then to be wrong._