Agree with CC. Most carbs today do not include any adjustable
jets (needle valves). If it ran once, and doesn't run well now, something is likely clogged.
When you open a carb, you usually do so by removing a brass bolt at the bottom of the carb bowl. This is generally also the main jet. There is typically a hole in the side of the threads that also feeds the idle jets.
Spray thru the main jet, and up the hole where it installs. Also, look in the throttle (engine) end of the carb's venturi. You'll typically see 3-4 small holes (hair-size) drilled in a group where the throttle butterfly closes against the wall. These are fed from the main jet, via the hole in the side, as mentioned above. You can spray in the hole that feeds them with WD40 or similar, and you should be able to see it come out those transition holes in the venturi. If not, there's a clog in that passage. It'd be accessed by removing the welsh plug in the outside of the carb body, just outside those transition holes.
Believe that's where the trouble would be.
Other possible issues could be a worn throttle shaft (causes air leak), or a poor gasket seal between carb and engine somewhere.
Failing that, as CC observes, replacement carbs are cheaper than you may think today.