Well you started off saying it was not running
And valves can be open too far or not opened enough
A common problem is setting the valve lash on TDC exhaust stroke not compression stroke .
I check the ignition timing if the coil is suspect by putting the piston at TDC then painting a line on the flywheel where it passes the edge of the magneto
Thus use a timing light
The light should flash before the line gets to the magneto .
