Glazed cylinders are caused by heat and small worn bits of metal plugging the valleys between high points. For the life of me, I don't know how an engine can get glazed with lots of raw fuel and oil pouring over the cylinder walls. Running excessively rich should only be done for a tank or so and helps to prevent the engine from overheating, washes out any worn metal, and helps to seal the rings which means more compression which in push's the rings out against the metal.