I bought a used Airens Max Zoom 60 ZTR with a relatively new Kohler CouragePro 25, had it repaired including a carburetor rebuild, and have run it for probably 10-15 hours. It just quit after about 15 min. of running. I tried to restart several times up to a four hours after it quit with the same result: no engine turnover, no clicks, nothing. It quit a couple of times before; the first time it started back up after a couple hour rest, the second time, it started up after a few minute rest. Help!