Bad throttle cables are pretty obvious with the exterior coating cracked and the inner cable exposed. When that happens moisture can get in and start having the cable become very stiff and possibly jam. If the throttle cable looks good & allows the carb to return to idle as well as allowing the carb to go to wide open position when the gas pedal is stepped on to the floor... then I would not replace it. There is a long metal sleeve on the carb end of the cable that allows a little adjustment to ensure the cable both allows the carb to return to idle as well as permits WOT.