What you got there?
A piston engine!

Try the pinch test...
When it's idling, pinch the fuel line near the carb. and see how long it takes for the engine to quit.
If it quits almost immediately, it's too lean...
If it takes more than about 5 seconds, and the r.p.m. goes way up as it dies, it's too rich...
You want the r.p.m.'s to pick up a few hundred or so, and then quit after about 5 seconds.