It could be a weak spark. Something a new properly gapped plug might
help.

Before adjusting a carb a good practice is to fully seat each screw
and record the number of turns so you can start that way again after
disassembly.

Typically the smaller fuel screw is set at about 1.5 turns, the larger
air screw at about 3.

I suggest, setting the carb, drain the crankcase and try the starting
fluid. (Don't use it too much because it has no lubricating
qualities).

If it only runs with starting fluid, there is something wrong with
your carb.