Small Engine Troubleshooting Problems? Ask a Mechanic Now.
get a new key switch, and if the battery continues to go down when it sets, replace the voltage regulator. Regulator can have a bad diode, and will let the battery discharge through it.
Do you know where the fuse for the ignition system is? It may be blown and not letting the key work the starter.
I see question is still open. Did keyswitch take care of probem? If not, did you check the voltage regulator?