As Bill says. I can send you detailed instructions on adjusting the valve and or a Service Manual IF you like. Address below, put in proper format and remind me, engine model number and what you want. Walt Conner wconner5 at frontier dot com

Buy a can of spray carburetor cleaner. With the air filter cover off, spray about a one or two second burst of the carb cleaner into the carburetor throat. Then try to start the engine. If the engine starts and runs for about 2 seconds each time you spray the cleaner into the carb throat....your no start issue is due to no fuel delivery from the carb to the intake. If, however...the carb cleaner does not provoke the engine to run (for a couple seconds) that means the problem lies elsewhere. Bear in mind, the mere presence of a spark does not mean the spark is happening at the proper time. It is possible that the first episode of trouble, resulting in some "back firing" may have partially sheared the flywheel key, which would put the ignition spark timing to something other than the proper time. But don't go yanking the flywheel off yet. Let's see how it does on the alternate fuel (carb cleaner) first. Then we'll go from there to a next step.

You probably need a test light to see what is going on. I agree with the previous suggestions that wrong parts may have been installed or connected improperly. Check ground wires for continuity. Also look at the safety switches to see if they are adjusted or packed with grass. Problems like this require in depth knowledge of the electrical system. This was a very nice older mower that is well worth maintaining. The horizontal shaft engine has been out of production for about 10 years. The blower housing and baffles on the engine should be removed to clean the cooling fins.

Cudo's to both and Walt & Tom they have assisted numerous forum members (myself included) within their expertise . I know they will be quite happy that you took the time to respond accordingly .