Starting Problem

Hello guys. I have a strange (to me) problem that has me stumped. I bought a John Deere Z 245 zero turn mower off a guy that would turn over but won't start. He had replaced the carb with a new one, new fuel pump with new fuel lines and cleaned the fuel tank. It will start and run on starting fluid as long as you keep spraying starting fluid it or the breather housing. I personally went back starting at the fuel tank and tracked fuel from the tank, visually through the fuel filter and assured positive fuel output threw the fuel pump to the inlet on the carb. I removed the carb and fuel is in the bowl and has made it all throughout the carb. The engine is evidently not pulling fuel through the intake and into the combustion chamber. My question is could the rings be wiped out causing the piston ring cylinder wall interface to be inadequate in causing an adequate negative pressure environment inside the combustion chamber to draw the fuel in? I may be way off base here but I have reached the limits of my knowledge and ability here. Any guidance or ideas on what could be causing this thing not to run would be greatly appreciated.
Thanks
Engine info:
Briggs twin cylinder
Model 44L777
Type: 0144 G1

Starting Problem