A few things to consider when inspecting the valve train: Verify that the rocker studs are both tight, that both valves actuate about the same amount and return to the same position competitively and that the valve guides themselves protrude similarly from the head.

Have you checked for spark when the engine wouldn't start? Did you also check the choke linkage to make sure it is working properly?

Try starting it several times and if it doesn't start check the plug to see if it's wet with fuel. If dry, pour a small amount of fuel in the spark plug hole , install the plug quickly and try starting again. If it starts you can rule out an electrical problem and may be a valve or fuel problem. You may also try loosening the gas cap to see if a clogged gas cap vent is causing the issue.

Picked up a spark tester and verified the magneto was inop with and without the kill wire connected. I will get a replacement for the brand new magneto and try again. I will post the result when finished.

Replacing the magneto should solve your problem, their failure is quite common. Another indicator of a failing magneto is it will start properly, then when the engine warms up the heat causes failure and it will not start again when warm.

When you install the magneto use a business card to set the air gap between the magneto and the magnets on the flywheel, ten thosands is a good setting. Let us know how you made out.

Swapped out the magneto and checked for spark. All tests were satisfactory but it would not start. Just spun and spun. I hooked up a compression gauge and saw it was extremely weak. I took the valve cover off and the cap on the intake valve had fallen off. Readjusted the valves and then went to start it and everything worked. I let it run for 30 secs or so and then stopped the engine so I could get the mower out of the garage. (Had others things blocking the exit). Got outside and attempted to start and the motor just spun. After everything cooled I took a look at the valves just to make sure everything was okay and it was. Now I am perplexed. I will take a another again at the plug for signs of fuel and the fuel cap to see if that works and will post the results. Thanks for the help this far.

No start. Double checked the fuel bowl, it had fuel. The float and needle were replaced. Cranked the motor a few times, the spark plug was wet. Motor just spins. It does not get stuck nor hesitate when the compression stroke comes around (which it used to do before all this occurred). Even tried a squirt of starting fluid with no luck. Not sure where to look next.

If it doesn't seem like it has good compression yet, look close at the valves -especially if at TDC the valves don't protrude the same amount from the head. If compression seems Ok, double check that flywheel key. Maybe the flywheel wasn't secured properly.

Checked the valve clearance again and readjusted again just to make sure. The valves protrude and actuate the same amount. The pushrods protrude the same as well. Still no start. Currently charging the battery because I hooked up the spark tester and had no spark. Granted I have tried starting multiple times do the battery is weak and I may not be getting the minimum speed for the magneto.

If you're not receiving spark it's quite possible the grounding wire going to the magneto is grounded all the time. Thast wire goes to a switch that is grounded. When the switch is activated it sends a ground to the magneto and it won't produce a spark. When the switch is deactivated the magneto is not grounded and a spark occurs. Trace the wire going from the magneto going to the stop switch and make sure it's not frayed or pinched.

It's a little more work but to verify the wire or stop switch is bad remove the ground wire going to the magneto, reassemble and don't attach the plug wire, then see if you have spark. You can also try to start it and if it runs you will need to choke it to shut it off.

If it works properly you now know it's a bad ground wire, defective or misadjusted stop switch.

I removed the grounding wire from the magneto and still no spark. Two weeks ago after putting the second new magneto on I had spark both with and without the grounding wire attached. I find it hard to believe that a second magneto would go out that quickly. I double checked the gap and it is per spec. Thoroughly confused at this point.

I too find it strange that the second magneto is not producing spark, however, anything is possible.. If you disconnected the ground wire to it and gaped it properly using a business card, you are eliminating any possibility that the grounding circuit is the problem. You should set the gap where the magnets on the flywheel come in contact with the two legs on the magneto.

Did you also check the flywheel to confirm the magnetic contact surfaces are still magnetized?

Gapped the magneto again. The magnet on the flywheel is still magnetized. It pulled the magneto nice and tight to the business card when I gapped it. Still no spark.

If you've set the gap on both legs on the magneto correctly, don't have a sheared flywheel key, and have disconnected the ground wire to the magneto you should be getting spark. Although it seems unlikely, the replacement magneto you purchased may be defective.

Sorry but I'm all out of ideas, maybe someone else can offer better suggestions.

A) That mag is installed flipped or B) You may be feeding voltage into the kill terminal. Even for moment such as from a funky ignition switch will kill these new style coils. Using a booster? That too can push power through where it is not wanted.

The mag is installed correctly. I had read about the voltage going through the kill wire. How do you check for that scenario? I did pull out the ignition switch and the continuity checked out okay. Haven't used a booster thus far.