Onan 4ky generator

Then let me offer a warning about "flywheel magnetos." The flywheel is keyed to the crankshaft to allow the magneto to properly charge its coil and possibly also provide correct timing.

If you want to check the magneto, OK to put the flywheel on (using the Key), and spin the motor WITH NO Spark Plug. If you want to check WITH a Plug, TORQUE that flywheel nut to specifications. If the engine fires, even just once, that impulse will shear the Key, damage the key-way in the Crankshaft, or crack the Flywheel.

I should have called it a magneto but called it a coil. I believe your right it had it out of time. I couldn’t figure out why it was back firing.

Kpackpackkelley wrote:
...Turns out after we pulled it and installed a new coil it started right up...

Good troubleshooting! Sometimes a part can "test good" yet not work, but swapping in another part that tests the same will solve the problem.
I didn't look at the 4KY parts list, but I'm guessing this is one of what I'll call "all in one" coils where the rotating flywheel not only charges the coil, but also provides the timing signal. If so it could easily be "half bad" with Good Spark but Wrong Timing, and/or Correct Timing but Bad Spark.

For those of you reading this who have 4KY's, always remember The OIL. Over the years we've had many of these lose an engine because the oil was low. Maybe because the oil was cooked to where it wasn't oil anymore. This is a high RPM, splash lubed, air cooled engine and not at all forgiving. Like your lawnmower. Unlike your lawnmower, it runs half a day instead of half an hour. Runs unsupervised instead of you right there with it. Inconvenient to check/change oil instead of pretty easy. Very expensive instead of expensive enough.

I have now had three HEI coils that failed partially and suddenly. This is no real surprise to me.

Matt