Small Engines (Lawn Mowers, etc.): Will not start after trying everything, spec number, proper fuel

Question
Dear Sir,
I have a Kohler KT17QS, spec number 24167, that is 10+ years old. I have been running it since mid February while waiting on new deck belts. I was just riding it around the yard to get it ready for the mowing season. However, it was running a little rough. I kept trying to adjust the carb to adjust it out and it seemed that that was not getting any better. So I cleaned the gas tank, replaced the gas hose, and installed a carb kit, basically replacing everything but the float. Cranked it up again. No change. So I checked the spark plugs. One ok and the other not so good. Checked the plug wires and found one faulty. Replaced bad parts and turned the key. Nothing, except the sound of the engine turning over. Replaced the other plug and wire. Nothing. Checked the points, firing. Checked the plugs against heads, firing. Put a little gas in the chamber. Nothing. I have a half of a tank of gas in the tank. The shutoff valve is open. And I do not know what else to do. Any suggestions?

Answer
Hi Ron,

It sounds like you are able to troubleshoot and do repairs well.  You are baffled and so am I.  If you have spark and fuel, which you do, then the engine should fire.  Proper fuel, timed spark and compression are the 3 and only things needed for an engine to run.  The timing should not have changed and neither should the compression.  With fuel and spark you should at least get a pop.
With no other ideas, I would have to say, check the compression.  Maybe a valve is sticking.  Coincidents do happen.  

Let me know how you make out.

Good Luck,
Michael