In the times of 50cc road races you could get 10hp out of it, at maybe 17.000 rpm :) No idea how fast these cars would go with such an engine, they are not made to go 150km/h :) The way you tune a 2-stroke is by polishing the ports of the cylinder to have an almost perfect airflow. In the Netherlands this happened a lot in the sixties and seventies to ride at illegal speeds with your moped, it was considered a craft. In the eighties people just bought a replacement cylinder to go at illegal speeds.

https://en.wikipedia.org/wiki/50_cc_Grand_Prix_motorcycle_ra...