[buster73]

Wow - looks like you had a nice carb fire melting down the inlet trumpets. You can consider yourself lucky the fire did not spread any further. Could be several culprits like sticky needle valves, heavy backfire and/or any other type of fuel leak inside the carb. Ignition should also be checked. Make sure to disassemble the carb and check what else might be damaged inside. Molten metal might have even reached the inlet valve or cylinders. The black tar-like substance might just be the remains of the smoldering fire, so just developed during the fire. One other possibility would be collected oil residue from the vent hoses at the back of the air filter housing. However I would expect this to look similar on both banks. How does you air filter insert look like ?