MTD Mower Keeps Draining Battery?

1. I would have the battery checked to see if it indeed drained.
2. What kind of engine do you have.
Reason I ask is I have a John Deere L120 with a Briggs and Stratton engine and it would not start. I though it was the battery. I had it checked at a battery store and they told me it had a full charge. They told me there may be an open ground on the mower. I bought a new battery with more cranking power. I installed the new battery and not even a burp from the engine. I asked a JD dealer what could be the problem. He said the valves were out of adjustment. ( Two dealers have told me the same thing.) He explained I had a Briggs and Stratton engine and they have made junk engines for the past 10 years.

He gave this bit of information for me to try. On the top of the engine is the air intake screen. With your hands move the screen in reverse or counter clockwise until you have resistance to the turning. Stop and try starting the mower. It worked for me. So every time I want to start the machine I have to counter turn the air screen untill I feel the resistance. Then it starts. As for the open ground,I checked all the connections as well as the safety connections and found nothing. Maybe this will be of some help for you.