The turbofan acts in the same way as a supercharger in a 1:1, except of being driven by a belt, it's drivene directly by the crank and is there to compensate for the loss of power due to the drag of the pullstart parts, but it doesn't, it really is just a fancy one way bearing to crank adaptor, which is the most common failure on these engines due to the poor material used, when the mills flooded and youtry to turn it over, it is this part that cracks and splays open allowing the oneway to revolve inside it and thus NOT turn the engine over. The only thing the fan really does is stir the mixture up a little more than a normal engine and so creates a better mix of fuel/air to enter the chamber.