If the spark plug is out, it should turn over like cake.
I'd take the clutch cover off and the clutch; Then check the main shaft, counter shaft and then pull the flywheel cover and see how it turns over.
Sounds like something is binding, maybe a thust washer in the wrong place? or a top end issue.
I'd check each item as I tore it down to narrow down whether it's in the center cases, the outside (kick/clutch side) or the top end.
I've seen binding simply in that external kickstart assembly, the guy didn't use a gasket and it was tight when kicking over.
From your description, it sounds like something is wrong.
All our government does is distract us while they steal from us, misspend our tax $ and ruin our country