Both carbs have small internal filters, they must be removed and the fuel connection side disassembled in order to inspect these thimble-shaped filters. It's quite common for them to be plugged with gum and trash that eventually makes it's way through the external filters, especially if that fuel is delivered using the Tempo fuel lines.
While the carbs are off, disassemble completely and give ALL passages a THOROUGH cleaning with carburetor solvent chased with compressed air.
About the only thing you don't need to disassemble are the choke and throttle butterfly shaft assemblies, leave them alone!
Also, if the fuel lines have been replaced recently and carbs already cleaned thoroughly, then you could start with pressure and flow testing the fuel lines from the carbs back to the tank. Any pressure leaks or restrictions in the fuel line will also cause a lean bog condition, leaks will cause the fuel pump to suck air as it draws fuel from the tank, air bubbles in your fuel will cause fuel starvation and the symptoms that come with it, such as your problem description.
Grey Tempo fuel lines though, are your clue the fuel system needs a full service help.
