That 13.5mm carb is a bit large for a Ryobi. Also, the larger carbs flow a bit more fuel stock, and may not need the regulator lever raised, especially when used on a smaller engine. My Poulan 42cc with a 13.5mm carb was blubbery rich after I raised the regulator lever. I put it back to stock and the engine straightened right out. I'm betting you are too rich, and the glow heat is covering it up.

You might also try a different glow plug in case yours is not "happy."

AV8TOR