I'm just going off of what you told me; I'm not trying to manipulate the situation.
Cheapest and quickest method will always be to use a cheaper, more advanced, mass-produced small engine from Asia, but are you really learning anything by doing so? I say keep it, refurbish it whether it makes any logical sense or not and use it at least once. It is also by no means an ordeal to bolt and un-bolt it from the kart as desired. It's not like we're dealing with the complexity of automobiles here with hoses, wiring and all...
Those
marvel rods look promising. I'm gonna have to check into that option--thanks for the info.
I also noticed your seat back was missing in the photos. Is it missing in action or just not photographed? Apparently that's a separate piece that is fastened to the frame with nuts and bolts.
The flat canvas strap in the center of the seating area was a factory addition--something for the passenger to hold on with I presume.