I have a 2006 Toro LX460 riding mower with a 20hp Kohler Courage motor. It sat for two months in my basement through the winter. It started with one crank a few weeks ago and ran perfectly for a few minutes (don't think it is bad gas). I was cutting the grass at wide open throttle with the blades engaged. I am uncertain of the exact sequence of what happened next. I wanted to get off to move a tree limb out of the way, and cannot recall exactly what I did (may have put it in neutral with the blades still engaged?), but the engine speed dropped to idle without me touching the throttle. I moved the throttle from low to high and this had no effect on the engine speed. It sat there and idled for about a minute before I decided to kill it. I have been unable to get it started since.
This is what I have done to troubleshoot the problem:
Pulled carb apart and cleaned it - no visible debris that I could see
tested the fuel shut off solenoid - good
tested for spark - good
sprayed WD40 into the carb while cranking it - causes a backfire but does not sound like it wants to start
I think it may have something to do with the governor. I went to Home Depot and found a Cub Cadet with a Kohler engine that had the same looking throttle mechanism as mine. When I moved the throttle on it (while engine was not running obviously) the governor arm moved too. My governor arm does not move when I move the throttle - unsure whether it should. I can see inside the carb and the inner butterfly does not move with the engine off, nor does it move while I operate the throttle lever while trying to crank it.