Still puzzling about the yellow oil patch. If you are in the habit of filling the oil up near the top of the sight glass it tends to blow out the crankcase and back into the air intake, then out the tubes. If there's more oil in the crankcase than you thought and it smells like gasoline you may have a stuck carb float letting gas into the engine and down into the crank. A lot of the guys on this site and the owners manual says to shut the petcock off between runs to avoid that problem. Hopefully that's not what you have going on.