MAX-75AX 12.29cc 2-Stroke Engine w/ SilencerO. S. MAX 75AX 2 Stroke 12. 29cc Airplane Engine (with muffler) Power up your big bird the easy way: simply swap out your MAX 61FX with the awesome MAX 75AX! It uses the same same bolt pattern, so theres no modifications required to mount the 75AX instead of the 61AX. The angular head not only looks sharp, it also significantly increases surface area for better cooling. A diagonally positioned needle eliminates the need for a remote needle valve.