Well, if it's not running, or was smoking like a big dog, just pull the head off......it ain't gonna fix itself.
But I digress............
I use a cyl leakdown tester, but you can check it with just an air blowgun.
Pull the valve cover.
Bring the piston up TDC on compression stroke, hold the flywheel/crank securely( however you wanna do it) and push a little air in the spark plug hole, and listen for air in the pushrod galley and/or all around the outside of the head.
The Slapper, AKA Mr. Kohler, might be able to offer up some ideas...........