The coil on the Ryobi is rather weak to begin with. You have to have the plug gapped at .020" and the coil about .010" or less but don't let it hit the flywheel.

Then wait till there is a night with no moon. Take the plug out and fasten it to the motor on the out side where you can see the electrodes. Then spin the motor over with an electric starter. You will see a little short duration yellow spark come out of it. You will unlikely ever be able to see anything by turning it over by hand.

It is really not that unusual for a coil to go bad. You'll need another to try on it if you are not getting any spark. I had a Walbro go bad on a Homelite. It would make a spark in the above situation but was intermittant when running. New coils are expensive at around $40.

The Walbro coils are a lot hotter if you could find one that would fit. Don't know that they ever came on a Ryobi though.

If your looking for another junk Ryobi engine to steal a coil from, don't forget that there are other names on those. Lawn Boy, Ryan, Sears, Toro, and others. Some Ryobi coils have RPM limiters in them that won't let the engine run much more than 7,000.

Good luck,

Jim