Satoh S-650G won't start

[AcmeDave]

My Satoh has a 4-cylinder gas engine. Over the past year I've replaced:
- Fuel lines, filter, fuel pump, carburetor
- Spark plugs, wires, points, condenser, ignition coil
Each time it ran a little better or worse. The last thing was the coil which did wonders. Now it won't start at all. Not even a pop with ether.
I find a spark on each cylinder. The timing is right on. Good gas flow. Well charged battery.
Not even a cough! What am I missing???

 

[Tinhack]

Have you tested the compression? Low compression may be caused by bad rings, valve adjustment or burned valves.

 

[AcmeDave]

Checked compression: A solid 20 psi on all cylinders. Head gasket?

 

[claggstractors]

Have you checked the valve lash?