Use a bright light and a magnifier to look through the jet. Spray out the holder with carb cleaner and examine it the same way although you cant see much more than the holes drilled cross ways through it.
I added this again as you did not mention it:
Make sure you have good gas flow with the gas line disconnected, you can disconnect the banjo at the carb. There is a filter screen inside the tank around the pet cock. Also, look inside the Bolt which holds the banjo to carb, Mine has a small screen in there which can reduce fuel flow.