Go ahead and get a Saito or OS 1.20 four stroke, as nothing can beat it for sound and smooth smooth running. You definitely don't want a gas (two stroke) engine in this one, as it will take too much away from the scale authenticity of such a pretty scale model. If you don't want glow, then get one of the Saito gassers. The new OS 40cc gas four stroke would be way too much for this model, but I've heard through the grapevine, that they will have some smaller versions in the near future.