If its an OHV engine, I'd suspect a sticking valve. Is the zone control fully disengaging the switch?

I have decided that the compression is too low on my mower so case is closed, Thanks

Like Tom advised could be simple as a carboned up exhaust valve , especially with the low compression !

My shop is at 7,250 feet. Brand new mower engines ususally have about 55 - 60 psi at this altitude and have no problems starting. If you live at lower altitude, there is probably something wrong, but the engine should start. the checks below are quick and easy.

you did not identify what engine model you have. IF this is OHV, check the push rods to make sure they are in position. Sometimes the intake valve sticks and the pushrod falls out of position. I have tested compression on engines with this condition and find about 50 psi. A blowdown compression test will help.

If this is the flathead quantum, pull the top plastic cover or the metal brush guard. This will allow you to observe the air vane and choke operation. Since you are getting a PUTT-PUTT, the engine may be flooded. Remove the air filter housing so you can actually see the choke. Manually hold the air vane forward or toward the sparkplug. Ask a helper to pull the starter cord and see what happens. This should clear the flooding. IF the engine does not start, prime with some fresh fuel and see what happens. If the engine fires, chances are the carburetor still has some old fuel or the main jet is partially plugged.

May be a good idea to check the ignition. Use a spark tester with the .166 gap. Also sparkplugs with a lot of carbon may not jump the gap consistently.

Blue mower where you been hiding these days ?