It just stopped like you had turned off the key

[Lazer dawg]

2006 lazer Z. 820+ hours...really no issues to speak of till now. Always serviced and maintained by the book. Was mowing and 25 hp Koehler engine just quit like you had turned off the switch. Checked fuses and wiring seem to be good. Installed new spark plugs and getting fire on both sides. However pulled plugs back out. One side clean the other black.

The engine turns over but will not fire. Tried starter spray nothing

Any suggestions? Why would new spark plugs, after turning the engine over a few times, be black one one side and clean on the other?

 

[logert gogert]

sounds like the cylinder with the black plug is running rich or some oil got in there, try pulling out the plug, clean it, and turn the motor over without plugs in there.
insert the plugs back in and try to start it.

 

[Joe Kuhn]

Had a dead Craftsman rider that behaved like yours. Would not start at all, even with starter fluid. Hand over air intake showed no suction at all. What what you get on yours.

It was a bent valve lifter rod. Took the head off it and replaced that rod and was good to go once again. Didn't even pull engine.