ROUGH IDLE

Make sure the idle is at specified RPM when adjusting the idle mixture screw. Once the RPM gets over the idle speed, the idle circuit is bypassed.
Take the screw out and make sure the hole is clear. Screw should not have any scoring.
There are 2 holes in the bore, one at the idle screw and one above. The above hole should be clear.
The idle tube should be clear. This is the tube that screws into the float bowl with the top off.
There is an air bleed hole in the bowl close to the top of the idle tube. Make sure that is open.
Perhaps the throttle shaft is worn and leaking too much air. Use carburetor cleaner and spray around throttle shaft. If the RPM smooths out, you found a vacuum leak and will have to re-bush the throttle shaft.
Was the throttle plate removed & replaced? It could have been installed backwards.
A strong smell of fuel could indicate a flooding condition.
A rough idle can also be caused by a vacuum leak. Spray carburetor cleaner around the mounting gasket, intake manifold and any other vacuum source.

IDLE MIXTURE ADJUSTMENT