ORIGINAL: Konrad
Opening up the air bleed limits (deteriorate) the engine's ability to draw fuel fuel from the tank. This is why the Fox line of engine is so superior to some of the popular asian brand entry level engines. As all Fox RC engine come with an auto mixture carb of some sort, even the little Fox 0.15 BB R/C. They all draw fuel better than any true air bleed carb at idle.
I don't understand why you constantly have to keep picking on other brands all the time, are you even running any of the small glow engines yourself?
There are even engines that are smaller in capacity then the Fox .15, they are made in asia, feature true ABC and have twin needle carbs etc.
Back to Fox, there are two obvious design flaws on the .15BB model as I see it. The head with a poorly fitted regular glow plug, and the poor design in the inlet area of the crank (ends forward with the threaded prop bolt). It is still a fairly decent sport engine though. The best running engine on 80/20 that I have seen in this size-range is the Webra 1.8cc Speedy, but it also features a glow head rather than a glow plug.