Welcome to the forum
I assume you are looking at the Chinese 2-stroke kits? I'd go with bicycle engine kit, bike engine, bicycle engine, bicycle motor
or Spooky Tooth Cycles - Motorized Bicycles: Gas Powered and Electric Bikes - Home
And to find the demensions of the frame you will need check this thread http://motorbicycling.com/f3/what-ki...mmend-510.html
Have any questions feel free to ask, always someone here willing to help out.