I have been using Amsoil 2000 in my bike for a long time now, and I haven't had any problems with excessive smoke. In fact, the bike hardly ever produces much smoke at all; just a little puff now and then, even with stock jetting. Then again, I do an aweful lot of high speed/ high RPM riding too. Over the winter, my motor was just taken apart for the first time since it was new in '97: from my findings I can say that Amsoil products mixed at 40-50:1 do not cause excessive carbon buildup in the powervalves. In fact, my powervalves were cleaner than most of the pictures I've seen of powervalves that have had a lot less time on them.
Summing up, in my experience/situation Amsoil 2000 is an exellent oil for low smoke and little carbon buildup. Your results may vary...
Regards,
Lutz