I have a 1988 John Deere 265 lawn tractor with a FC540V 17 hp Kawasaki engine. The other night I was cutting the grass and turned on the headlights and the engine stalled. I cranked it back up and it happened again. I have replaced the battery and it still does it. It now stalls when the blades are engaged. The engaging mechanism for the blades it electric also. It has a full tank of gas. What could be the problem?