i run yamalube 2s semi-synthetic on my motors, rc showcase had recomended that to me, they say it was one of the cleanest burning oils they found, and internally they look the best when they have taken them apart for other repairs, i have been using it for a year now and love it, very clean i think, it says for injectors on the labe but the back has the mixture chart also, i run 40:1, zdz says sstay at theat mixture for any in cowl set up, used penzoil 32:1 for break in, 4 gallons, but that was clean too i thought....just a thought, and the yamalube is easy to get for me, any yamaha dealer...here is a link to thier shpeal...
http://www.rcshowcase.com/html/accessories/oil.html