Kostas since you are an os man you should consider the magnums. they are clones of os and I bet they are just as good. magnum offer 70, 80 and 91 but since they are basically the same weight and physical size you should go for the 91. great cheap engine, I do own and run one and could not be happier. the 91 will give you more planes to choose for it later on than the 70. It does weigh just 640 grams muffler included, runs great on 5% too