While I was mowing today my Troybuilt Pony lawnmower shut off and I could not crank it. I pushed the clutch(brake) all the way down and disengaged the parking brake, I disengaged the blades and made sure the transmission was in netural and it still would not crank. Just before the mower shut off I was mowing about 6 inch high grass and the mower vibrated some. Can anyone tell me what to do now ?