It's nothing but bloody madness, largescale stated (1/6 at least) with the marder and most cars to date, come with a 23 or 26cc engine which if you look at most things on youtube is more power than most can handle anyway.
I would not have one of these engines as a gift - unless I could sell it and buy 2 proper engines from oddified or hobbycenter.
A good tuned engine isn't all about max out speed or torque neither is a big fat pipe thats louder than a loads of moto x bikes, all an engine like that will do is make you crash quicker and harder and eventually kill itself. A proper tuned engine and pipe are about being smooth and delivering enough power for the job in hand in the right place at the right time.
Reed valve engines work ok with good power but they've less mpg than a normal engine.