Check and clean plugs, mark distributer posistion, loosen distributer retainig bolt, while engine is warmed up and running, slowly turn it ccw tap the throttle, listen, should either get smoother or worse. If no change go back to starting point and rotate slowly clockwise. If it gets a little better in either direction, leave and try adjusting carb thrttle and mixture screws.
I've had pretty good results "ear" tuning a miss out of mine with this method... one of these days I will stick a timing light on it just to see how close I got. But it runs great, so no worries.
This is all assuming you don't have a vlalve problem, vac leak, loose carb as TJ mentioned.
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