J,
You can look through the plug hole, if you have enough light. The exhust is the best place to look with the plug removed. Homelite used a small hole above the exhust, half way up the cylinder. It went into the muffler. I tap the hole and plug it with a screw. Not so easy with the slots. There are so many venders and versions of the Ryobi, that it is hard to tell by model number etc.

Dave