I have the Magnum .52 2-stroke combo. Great engine! I broke it in as per the instructions and it runs like a dream! Lots of power for the Magic Extra but with a 12.25x3.75 apc it has all the pulling power you would need instead of speed. I've had Irvines, OSs, K&Bs, even MOKIs and this is Magnum engine is my favorite so far.