Hi
I am adding this for my husband, I will not know the correct terminology. We have a Sears B&S riding mower. Part number 40H700. We replaced the battery, but hooked it up backwards and it ran for a while, but then went downhill. Now it will start, and run, until you start to drive or engage the mower deck, then it wants to die out? He replaced the ignition switch, but no change. Any thoughts would be greatly appreciated.

Check the safety switch. And the battery must have been hooked up right, or the engine would have not started. Because the starter would have been spinning backwards if the battery was hooked up wrong if it didn't blow the fuse first.