Starting Issue

First time zero turn mower owner. husqvarna rz4219, hand me down from my father-in-law. currently has a starting issue. checked valve lash (.004 int &.006 exh). intake valve does that little jump, so i think camshaft is good. sparkplug looks fine. battery was hooked up to my car battery (car not on) while trying to turn over. not sure what the problem is. i dont believe any safety switches are the problem. goes through 1 rev and stops. any suggestions?

Could be hydro locked. The needle valve and seat in the carb may be not closing and letting fuel from the tank drain into the crankcase. Drain the oil and see how much comes out. If way more than normal, and it smells like gas, you’ve found the problem.