HI , yamaha oil is a good lube i sold it an used it for 20 years as a dealer , if the yamalube you are using is one of the synthic yamaha oils you want have to drain unless you just want to they will mix , excessive oil smoke is not usualy from ring seating in a two stroke engine , sometimes its from assembly lube , or the stroke on your oil pump adj , if pump has been setting unsued , sometimes they stick open from the old oils left inside pump , check pump stroke at diffrent throttle positions , thanks william anderson