I have a 2002 MTD Yard Machine with a B&S 18 hp. with an electrical problem I think. When trying to start I am lucky if I get one full crank. Battery seems good. + and Grnd wires get quite hot. I even went direct to the starter with jumper cables from an auto battery. Still won't crank. Changed starter motors. still the same. Last time it ran it was running fine with no vibration and plenty of power. I have not hit anything to cause the crank key to shear. Any ideas out there? I would surely appreciate it. Thanks