Charge the battery.
A slow cranking engine is hard to start. Slow enough and it won't generate spark.
The flywheel has to turn fast enough so the magnets/windings can "do their thing".

Charging as we speak. Still mysterious about why it cut out so suddenly. The low battery after running for about an hour suggests that the alternator might be weak but I'll deal with that later

I suspect a wiring or switch problem is allowing battery current to reach the ignition system which will destroy the electronic ignition - (CDI)

After charging battery, see if you have any ignition spark when the engine cranks normally. Remove spark plugs to let it crank faster if necessary.

Walt Conner

I agree with your statement, Walt. Another thread here described the same scenario. I'm an electrical engineer and I understand well what would happen to the magnetron if it gets battery voltage to it. I had a hunch that this was the situation but it's good to hear it from others.

It may not be a bad idea to do a test run with a voltmeter on the disconnected kill wire to see if something may be intermittently be sending voltage. Unfortunately, there is scuttlebutt that the new design Chinese made Briggs coils can fail w/o external cause. I've had two fail and I know of others in other shops nearby, so I don't think they are having just an isolated failure. If I have another, I think I'll go to aftermarket for a while.

tomplum, do you have any recommendations as far as aftermarket versions that might be appropriate?

I don't really. I have snuck a Stens or an OEP on a parts order when I wasn't ordering from the Briggs distributor quick enough and had no problems though. At least in recent history. I liked the OEM coils as there was I time 10-12 years ago when I could't get the OEM coil and had to use the Oregon and did have a bad one and swore I wouldn't go back because it ended up being a thorn in my side. Given the choice, a NOS 394891? was the best coil if you could find one.

Thanks tomplum. I will check that out and report back my progress. I don't get to play much during the week so it will be weekend at the earliest.

Bypassed the ignition switch and made up my own OFF-ON with a separate pushbutton start. Didn't solve the magneto issue so I bought one from Oregon. Tractor started right up after installing.
Thanks to all for your help. B&S is checking the magneto for defects. Will post once more when I learn the status.