If it won’t start up with starter fluid sprayed into the combustion chamber then you do not have a fuel delivery issue and replacing the carb is not likely to solve the problem. Maybe you need a new carb anyway, but you would get to the ultimate solution faster by pulling the kill wire off the coil and then trying to start the engine. If it starts, you would then know that the spark is grounding out and you could look for the switch or wire that is grounding the spark. (Always make sure you haven’t left the pto engaged as that grounds out the spark via the safety switch.) If it still doesn’t start with the kill wire off then you know it is either bad compression or bad ignition timing. Bad compression could be caused by out of tolerance valve lash or worn pistons. Timing is set via the flywheel and a woodruff key. Engines that have fuel, air, compression, and spark delivered on time will run. Simple as that. Eliminate possible suspects and move to the next, you’ll find the cause of your non start condition.