See below for CL ad. Worth the gamble at $100 or so offer or should I avoid it? Sounds like the hydros are good, but that the motor maybe has a bad coil or really badly gunked carb. "Whirring sound" has me stumped, maybe sticky valves?
Edit: The mower is listed as a John Deere STX 46.
The 14 HP Kohler engine runs very well. It mows for a while an then makes a werring sound and slows down. It will not climb even small hills. I can't find anything wrong with it but there it is still with the problem. I am tired of trying to figure out what is wrong with it. Maybe you can. The mode is HYDRO. The black deck is very good and the blades are fine. The battery is OK. This riding mower has a broken hood. Tires are good, in fact everything SEEMS good except the broken hood. I don't think that the hood is fixable but it does go on and with a strap it stays. Please leave your phone and I will call you with answers.
Edit: The mower is listed as a John Deere STX 46.