Im in the same boat. Just had to replace the piston, and cylinder, and now i have to seat the rings in again. Im running 4 OZ synthetic 2 stroke oil, 1 OZ of MMO per gallon of gas. So thats about 29:1? No smoke, and runs well, and when i took it apart at 220 miles, was well lubricated, with no wear in cylinder, or carbon build up on piston. My take on break in is, vary the speed, no long wot runs but ever so often is good, run a slightly heavy oil mix, but no need for 16:1., dont rev it too the moon while going down hill, and remember to have fun!