what you said, use "normal" oil once and never agian the carbon build up was too much.
now i only use synthetic oil, here {honolulu} costs me $1.79 for a bottle that will fill up my oil resevoir. do not pre-mix on my Areo 50, or Spree. even both are modified, although i sometimes mix some with my gas anyways if i plan to do alot of riding.