Just an idea that Ill personally probably never do but seems like the end all be all. A lot of my friends have pitster pro pit bikes that have little 125cc four speed four strokes in them and they all run incredibly reliably and accelerate way faster than the short wheelbases can handle. So my question is has anyone done this or can it be done. this motor right here is only 250 dollars with a four speed!!
http://www.t-motorsports.com/li12enmohoxr.html
http://www.t-motorsports.com/li12enmohoxr.html