Like MMDEL recommends disconnect the fuel line and look for a SOLID stream of gas. If you find gas just sorta dribbles out, find and correct the restriction in the fuel line.
If you've got good flow, drop the carb bowl and thoroughly clean the insides. Pay particular attention to the power jet at the bottom of the bowl (where the power mix adjusting needle fits into). Clean/blow out all rust and other debris here. Better yet, remove and disassemble the carburetor. Give it a long soak in a good carb cleaning solvent then blow out EVERY passage and orifice.
Note the Marvel TSX carb on your UTS is as simple and about as trouble-free an old carburetor as was ever made. There's not a lot to go wrong that's not easily fixed!