I wonder if timing is messed up. I just checked the engine and this is what I found:
1) the flywheel is sitting nicely in the notch on the shaft
You timing should be fine as Edwin mentioned.
I have Ryobis some with A) a physical metal key (about 1/16" wide) which fits the slots in the shaft and flywheel; some of the others B) have a cast key protrusion in the flywheel taper which fits into the slot in the shaft (about+-1/8" wide) Unless the was not installed in A or B) cast key has been sheared off, it is almost impossible to put the flywheel on out of time.
Is your engine mounted in the plane with the head(and plug) on the bottom (inverted) or top?
I have primed it by squirting sam gas into the cylinder or by sucking some gas through the primer bulb valve. I'm just sort of surprised that I get no ignition at all.
????? Is it possible that you have the fuel lines connected correctly? That primer bulb is designed to be on the downstream side of the fuel flow through the engine.
If you 1) set full throttle, 2) choke the air intake with your thumb, 3) rotate the prop 10 or so times you should have a wet thumb. If not you have a fuel supply /air leak problem in the fuel delivery system.