RE: 50cc engine choice
By the time all is said and done, the cost between the DA and the Taurus is pretty close. Power wise the Taurus may have an advantage, and the Taurus is definately a smoother engine. Both the DA and the Taurus are good choices, but it's my opinion that the Taurus has a superior ignition with the CH. The DA is very good, but the CH is a little better, IMO.
Dougtx
The first chance you get take a moment to work with the carb needles a little bit. None of the Taurus engines are adjusted at the factory for the end user, and are almost assured to be out of tune for your area. You may well be missing out on a lot of power by leaving it at factory settings, and have the possibility of causing damage if it's on the lean side.