MAX-120AX Ring 20cc 2-Stroke EngineO. S. MAX 120AX Ring 2 Stroke 20cc Airplane Engine (without Muffler) Perfect for sport and 3D flying! Admit it: if you could ratchet up horsepower without having to increase the mounting space, youd probably jump at the chance. Well, here it is. The 120AX boasts 25% more displacement than a . 91 and it bolts into the same space, with almost no extra weight. Plus, the angled heat sink head not only looks sharp, it adds more surface area, for better