Small Engines (Lawn Mowers, etc.): lawnmower, engine rpms, compression issue

Question
engine sat for 3 yrs. I cleaned carb, replaced points,reset coil = starts 1st pull but can't adj idle mix for smooth idle. when I turn screw it does change but never smooths out. any hints?

Answer
This really depends on what you mean by smooths out.  If the mixture screw does have an effect on the engine, the low speed circuit is functional.  You may want to attach a timing light to the spark plug lead and see if you have any ignition misses causing this (you will any missing fairly easily in the light).  If this is not the problem, you may want to suspect a compression issue.  Compression issues (burnt valves, etc.) are more prominent at lower engine RPMs.  Hope this helps.