How about one of those little Chrysler Hemi, Corvette, or Ferarri engines being mated with a transmission suitable for powering a moped?  A lot of those low-powered bikes are running on 49cc engines that are smaller than these, and I am certain they are less powerful also.  These little masterpieces of engineering skill ought to get put into mass production and put to widespread uses.

 Donna I know the article is under the heading "Just for fun" but it's a pity you lump this farce (Smallest petrol engine) in with genuine miniature engines that DO Exist, and actually run, made by real craftsmen.