To answer the question two professional cyclists completed laps of a velodrome and recorded their top speed and time over the last 250 meters of the circuit. On their track bicycles they both managed a top speeds around 65km/h, and on the mamachari they barely managed to reach 44km/h.
In contrast, a comparatively unfit member of the programs crew completed the same course on the mamachari and managed a top speed of 39km/h. Thus it was concluded that the top speed of a mamachari is more a factor of the bicycles gearing and geometry than the strength and level of training of the rider.
Obvious of course, but still entertaining viewing on a slow Wednesday night.