Poor Fuel Mileage

Ensure there are no vacuum leaks.
Ensure ignition and valve timing are correct.
Verify choke valve is open (engine warm).
Ensure fuel level is at specified mark on carburetor sight glass.
Verify base timing is correct and timing advance system is functional.
Ensure sufficient secondary spark is available.
Check canister purge control valve operation.
Ensure engine has sufficient compression.
Ensure exhaust system is not plugged.
Check carburetor mixture control duty cycle using dwell meter.
Check engine for overheating or overcooling.