your fuel has decomposed to a varnish like substance and fouled your carb.

since the engine does start and run, you may be able to clean it by using SEAFOAM in the fuel. it will gradually clear up.
the 10% ethanol in most fuels will not harm your carb.

before using a fuel system cleaner, like SEAFOAM, you should drain all the old fuel and add fresh fuel before treating.

your other option is to remove the carb and clean the jets by hand.

if your carb continues to overflow out the tube, you should remove the float bowl and replace the float needle. the rubber tip will harden over time and they do require periodic replacement.
let me know if you need more help.
Steve

that indicates your slow jet is fouled.

a fuel system cleaner will eventually clean it out, but if you need immediate results, I would remove the jets and clean them by hand, THEN run a fuel system cleaner for a few tanks to clean everything out.
here is a diagram of your carb showing the main and slow jets and their locations:


G is the slow jet, L is the main jet and the main jet holder.
there is a rubber plug under the slow jet passage.
let me know if you need more help.
Steve