if it's a ground problem, you have a good ground to the cab [probably where the batt is grounded], but you may not have a good ground to the engine, so the choke/throttle cables [grounded each end to the cab and engine] are carrying the ground for the engine [why they get hot is the starter pulls mega current] .... if this is the case, you would fix it by adding a ground cable from the same place the neg batt terminal goes to a starter mount bolt
if that's not the problem, you have an internal short in the starter - either way, putting enough juice thru those cables to heat them up seems a poor idea, considering they attach to the carburator, so I'd figure out the problem before cranking it anymore!!
Bill