Oh, I forgot to add - I've noticed a lot of carbon on the muffler. Do I possible have a valve clearance problem?

Have you checked for spark when it dies out?

Hi Mr. Buzzard. No, only because it's impossible to see the sparkplug when I'm on the opposite side of the tractor pulling the rope. I assumed changing a weak magneto would have taken care of that if it was my problem.

"Hi Mr. Buzzard. No, only because it's impossible to see the sparkplug when I'm on the opposite side of the tractor pulling the rope. I assumed changing a weak magneto would have taken care of that if it was my problem."

No family or friends? Anyway, you can take out the spark plug, stick a Philip's screw driver in the plug boot, grasp it in the palm of your hand, place a finger on the engine block in a bare spot, doing this while reaching around the engine and then pull the rope.

On the throttle box, where the throttle cable attaches, is a junction terminal. disconnect all wires from this being careful that now of them are touching anything then see if the engine remains running.

There was a lot of testing you could have done before buying anything.

IF not, I suspect a valve may not have enough clearnace.

Walt Conner

Thanks all for repsponse.

OK, assuming I didn't need to buy a magneto and safety switch interlock, and checking all wiring for breaks etc, what else would cause a no spark situation? Engine switch seems fine, although I didn't take it out and test it for continuity.

After I replaced the safety switch I was able to mow for an hour with no issues, plus the engine had more power thanks to the magneto and stronger spark. When I went to mow a bit in the afternoon it lasted for maybe 5 minutes before it shut down, this time surging. I think I had a confluence of issues, both electrical, fuel related and perhaps engine block related (carbon buildup and valves causing gas to boil in the carb body?). I don't know why it would run for an hour without issue then die suddenly after a 5 minute run. The spark plug doesn't smell like gas or have any unusual deposits...

"what else would cause a no spark situation?"

With that engine, only the flywheel and the coil are involved in making a spark when the Kill Wire is disconnected. Now, the crankshaft key is involed in making the spark at the right time and of course a good spark plug is needed to make the spark inside the cylinder.

Walt Conner

Spark plug is new. I checked all the kill wires for broken insulation, chaffing etc. No issues there.

Did a carb rebuild today (I didn't change out the main nozzle - it was stuck in there and I didn't want to ruin the seat). Engine seems to run a lot smoother. Maybe I had a lean situation causing the engine to overheat. I have to wait till some grass grows before I can see if that helps my stalling situation. If this isn't the solution I'll pull the head and look for carbon and check the valve clearances. At least it's free to look...

"I checked all the kill wires for broken insulation, chaffing etc. No issues there."

Does not sound like you did what I said and disconnect the Kill Wire from the base of the coil.

If so, sorry, can't help you further.

Walt Conner

RE: "Does not sound like you did what I said and disconnect the Kill Wire from the base of the coil"

I didn't do that only because the lawn is mowed and I didn't want to drive around for a half hour with the blades engaged hoping to duplicate the conditions that lead to the shutdown. I'll try that toward the end of this coming week.