A spark plug will set you back $3 or less, yet it's one of the most important parts of a small engine. Get one, they're not hard to find. On 2-strokes, they foul easily, too. You need a new plug for it to run properly. No clue on carb settings, though. If you had a Briggs flathead, I could tell you.
This isn't official, but once you get a plug, I'd try starting it (without the chain attached), run it at about 3/4 throttle, and adjust the high speed jet until it doesn't sputter. Then idle it to adjust the low speed jet.
You know, there are a couple steps between a 911 and a go kart. Like a 944 or 914.
