In shallow dish, mash bananas to a smooth consistency. In a bowl, dissolve sugar, salt and yeast in the water. In another bowl, combine banana, flour and yeast mixture. Stir the mixture until it has the consistency of pancake batter. Let stand 30 minutes. Brush skillet with oil. Heat until hot. Pour in 1/3 cup of batter. Cook pancake on both sides over moderate low heat until golden and risen. Continue with remaining batter. Serve warm with syrup.