From my 1970's engine class:
Intake-compression-ignition-exhaust
She's been working fine engine wise all this time, sometimes in extreme cold a shot of starting fluid to get going.
Now, engine won't start, working fine one day, nada next day.
I pulled plug, did the clean the plug with bristle and it back in, no start.
Replaced plug around least 1 year ago, so I'm guessing plug still good.
Pulled plug, had my son crank it as I watched for arc holding against cyl head... no arc.
So I'm guessing something wrong with the ignition ..
I checked to make sure all wires/etc are firmly attached, they are.
I've not dabbled with the ignition on this engine here, so advice is appreciated.