New battery,new plug, tried starter fluid, engine will turn but won't fire

Did it try to start pop or anything when you spray fluid in it,
And really I wouldn't spray starting fluid in it ,it could blow the head off.
Luck

Didn't pop or anything. The top of the motor just spins

I would take a compression reading.
Pull the valve cover and see if the valves are moving up and down.
Is this by chance a 18 horse biggs and strattion engine.