Timing or Carb Issue? Or both? Neither?

To check if it's running too rich or too lean, try closing the choke flap a bit or partially cover the air horn with your hand to see if it helps or hurts. If you suspect it's too lean, you can also dribble a little gasoline into the carb to see if it smooths out the idle. I use an old oil bottle with a pin hole in the top to use as a gas primer can and dribble tester.