Odd intermittent start problem with 5247. Spark then No Spark.

Kind of new here, been lurking. I got this 5247 (s/n 8294122) with a bunch of other things in trade for some work. I have used it on and off for 8-10 years but now would like to use it more. I really like it and appreciate it's light weight around our hilly terrain. It had a bad kill switch which I replaced with a standard, industrial-style toggle switch. I think the switch works but I have suspected it in the past. There will be times when it won't start and when I remove the plug, ground it and look for spark, I see nothing. I can come back the next day and it will start first pull. This has happened many many times. Once it's running, I can mow for hours; shutting it off, refueling, restarting, ect. If at the beginning of the day, it does not start first or second pull and maybe I flood it, I seems to have a no spark condition.
Are these ignitions sensitive to wet plugs where I would get this no spark? Should I get a spark doing the old ground-the-plug-and-pull-the-cord trick? Why would it start the next day on one pull? Thanks in advance for any help, C.

Check the kill wire from the coil to the kill switch. I'm thinking it is frayed and making intermittent contact with ground.

I went out there this morning and that darn thing started with ONE pull in NORMAL and TWO SQUIRTS on the primer. It must be a spark plug thing. Can you guys recommend a plug? I didn't find one in a search. C.

While anything is possible, it's unlikely the spark plug is intermittent or the cause of the trouble. The ignition is pretty simple, insofar it's a coil pack with all the innards inside. Guess I'd be inclined to make sure the coil pack is well grounded and the gap is set correctly. Not much else to go wrong. There is a batch of bum coils out there, or were. If you want to switch plugs - what's in there now? Try NGK, iirc BM4Y is the equivalent of Champion CJ-14, used in a bazillion LawnBoy mowers.