Give the float bowls a couple of hits with a rubber mallet. The floats may be hanging up on the gaskets.
+1, but gentle, NO hammer!
Floatneedles can stick. Remedy:
1) Tap the floatbowls (gently!) with the stub end of a screwdriver. If that doesn't help:
2) Remove the drainscrews and then open and close the petcock a few times. If you're lucky, in the combination with 1) you may free the floatneedles.
3. Add fuel additive to tank.
If that all doesn't help, remove the floatbowls for further inspection.
I have similar carbs and can do all maintenance with them in situ blindfolded. No need to pull the rack. Changing those awfull crossheads for Allen helps a lot.