I believe in missing kid karts and start teaching a young driver in a cadet chassis with a Comer 80 or the new Honda Pilot, It gives the new driver just enough power to learn braking aswell as throttle ( kid karts are mostly floored around the entire track).
Once a new driver gets some seat time on the Comer / Pilot, the next engine that we enjoy racing is the Vortex Minirok – Great Motor but more rebuilds. And of course the other great cadet engine is Rotax, very strong engines.
I think the IAME K-71 / HPV / KPV motors are steller engines that last a long time between rebuilds and fast.
