IF the carburettor has had stale/smelly discoloured fuel in it, it's likely one or more jets are partially or totally blocked. In my experince all the "mechanics in a can" will not unblock a carburettor in this condition.
You will need to remove the carburettor, dismantle it , as much as is practical, wash (even soak) each part with carburettor cleaner and blow with compressed air, to remove the fuel residue/varnish.
Check all jets, holes are clean of varnish.
In very gunked carburettors (residue has become treacle like or even dried) mechanical cleaning will have to be done ie careful "rodding" of jets with copper wire. Do not rod with anything that is likely to damage the jet or seat.
Professional workshops may use ultrasonic cleaners to clean difficult to access and or delicate parts.
