do you think a 12.5 hp engine could run an economy car rear axle with differential? or would it be too fast or slow? this is going to be an interesting kart
Depends on the gear ratio. You need to figure out the gear ratio of the rear end so you can figure out your ratio from the engine to the pinion. But it should work fine as long as the rear axel isn't too heavy.
hondas are light, and my 12 horse should turn it over nicely. it would be nice to have a torque converter. anyway, then i guess the trick is just finding one for a reasonable price. i guess if it is a widely manufactured car, the car it is on is totaled, and no wheels i bet ic ould get it like 100$ or less