To get a quick look at your AFR, you can take a non-contact infrared thermometer and compare the head temp to exhaust port temp. Higher head temp is richer, higher exhaust is leaner. This can be helpful because the plug can stay one color if it's not new.
Someone on here told me that, don't remember who. Thanks to them.
Hope the gas and some fiddling can help you out. Most small engines are tuned pig rich from the factory to keep them cooler and intact or whatever. The air filter/exhaust/ whatever else you've done has probably thrown towards the lean side if you haven't rejetted.
Heck, it's a four stroke, you could run an O2 sensor if you wanted to get fancy.
Logan