Red/black 12-volt Hobbico standard-duty starter is best on engines up to .90 cu. in. Gold/white 12-/24-volt Sullivan Super Hi-Tork heavy-duty is designed for engines up to 20.5 cu. in. Black 24-volt Model 4 Sullivan starter is for gas engines up to 2.4 cu. in. Green Sullivan Hornet starter is for .49-size engines. Photo courtesy Hobby Hut.