You are getting close to the last option-new. I'd be interested in how you checked the spark.
You should be able to tell if it's getting fair or better compression by the way it pulls.
Starting fluid under compression with the right spark, bang. One or more of those are not happening. I know you know that, but check em. Sounds like not enough spark to me. If it's the kind with the magnet on the flywheel, buff that off good.

I hate little bitty 2 cycle engines.