"The Life of Ramanujacharya" by Naimisaranya Das, published by the Vaisnava Educational Alternative (VEDA) in 1989. There are many nice stories in this book about this great vaisnava Yamunacharya (the predecessor to Sri Ramanuja).

In the south of India many great devotees have appeared to spread the glories of the Lord. Of all these devotees, perhaps the most famous is Sri Ramanujacharya, whose life is the subject of this book. However, just before Ramanuja there lived another great Vaisnava whose life and teachings had a tremendous influence on Ramanuja, although in fact the two of them never met. This was Sri Yamunacharya, also known as Alabandara – "The Conqueror". It is appropriate in considering the life of Ramanujacharya that we should first look briefly at this great soul, the illustrious writer of the famous Stotra-ratna.
Yamunacharya was born around AD 918 in the city of Madurai in south India, which was then the capital of the mighty Pandya kings. His grandfather was a well-known scholar and devotee known as Nathamuni, who was also famous for his mystic abilities and expertise in the practice of astanga yoga. It was Nathamuni who first compiled the songs of Nammalvara, a famous south Indian devotee, and had them set to music.
Nathamuni's son was a handsome, intelligent young man named Isvaramuni, who married a beautiful young wife. Shortly after the wedding, Isvaramuni travelled with his wife and parents to visit the holy places of pilgrimage in northern India, including Vrindavan, the birthplace of Lord Krsna. Just a few months after their return from this pilgrimage, Isvaramuni's wife gave birth to a baby boy, and, in memory of the sacred river which flows through Vrindavana, Nathanmuni named him Yamuna.
However, the joy of the young couple was but short-lived, for just a few years after the birth of the child, Isvaramuni passed from this world, leaving his young wife a widow.
Nathamuni was so distressed by the untimely death of his son that he decided to have no more to do with the affairs of this world. He left his wife and relatives to take up the life of a renounced sannyasi, totally dedicating himself to the worship of Lord Visnu. Thus at a very young age Yamunacharya was left to be brought up by his mother and aged grandmother, living a life of great poverty.
The Challenge
When he was five years old, Yamunacharya went to study at the school of Bhasyacharya and quickly won his teacher's affection, both for his sweet nature and his ability to learn quickly. He studied hard, and by the time he was twelve years old he was Bhasyacharya's best student.
In those days in India, great scholars used to challenge one another to see who was the more learned in Vedic scriptures and more skilled in the science of logic. While Yamunacharya was studying at the school of Bhasyacharya, there was a great scholar who lived at the court of the Pandya king. His name was Kolahala, and he was a great favorite of the king because he could defeat any other scholar in a debate. In fact, the king had passed a law decreeing that every scholar who had been defeated by Kolahala must pay a tax to him every year – if anyone refused he would be put to death.
Now Yamunacharya's teacher, Bhasyacharya, had also been defeated by Kolahala, and so he too was obliged to pay this tax. However, because he was a very poor man, he had not been able to pay for the past two years. One day, when Bhasyacharya was away on business and all the other students had gone home, Yamunacharya was left alone in the school. At that time one of Kolahala's disciples came there to collect the overdue tax from Bhasyacharya.
"Where is your teacher?" he demanded in imperious tones when he saw that Yamunacharya was alone in the school.
"Might I know, sir, who has sent you here?" replied Yamunacharya in a very gentle voice, anxious not to give any offense.
"What!" exclaimed the disciple, "do you not know that I am a disciple of the greatest and most erudite scholar in all of India? Kolahala is the terror of all other scholars, and even the great Pandya king is his obedient servant. All those scholars defeated by the great Kolahala must pay a yearly tax or else forfeit their lives. Has you teacher become insane that he dares to withold payment for two years? Or is it that he intends to challenge my master again, just as a moth rushes into a blazing fire."
Yamunacharya was by nature very kindhearted, and he hardly ever quarreled with his fellow students. However, he also had great love and respect for his teacher. Therefore, when he heard Bhasyacharya being spoken of in that contemptuous manner, he felt such pain at heart that he could not restrain himself and replied very strongly to Kolahala's messenger. "How foolish you are and how foolish your teacher is as well, for who but the greatest fool would train his disciple to possess such monumental pride, instead of removing such qualities from his heart. Why should my noble teacher waste his time debating with such a man? Go and tell you master that the lowest disciple of the great Bhasyacharya challenges him to a debate. If he dares to face me, let him send his reply at once."
Kolahala's disciple was so astonished and indignant that he could not think of anything to say, but left in a furious rage to inform his teacher of this insult. When Kolahala heard what had happened, he could not help bu tlaugh on hearing the age of his rival. The Pandya king decided to send another messenger to the boy to see whether he was insane, and, if he was serious about the debate, to bring him immediately. When the royal messenger came and told Yamunacharya of the kings command, the boy replied, "I will certainly obey the command of his majesty the king; but if I am to be accepted as a proper opponent of the great Kolahala, then surely a conveyance should be sent to bring me to his palace."
After discussing Yamunacharya's reply, the king and his courtiers agreed that the boy's statement was fitting and sent a costly palanquin and one-hundred soldiers to conduct him to the palace. In the meantime news of these events had spread all over the city of Madurai, and Bhasyacarya heard the whole story as he was returning home. He was very unhappy to learn of the danger his favorite student was facing, for though the king was generous by nature, it was well known that he dealt very severely with anyone who insulted the court pandita.
Yamunacharya, however, was not in the least concerned. "There is no reason, revered sir, for you to be alarmed," he consoled his teacher when he returned to the school, "for you can be certain that, by your grace, I will smash the pride of Kolahala".
While they were thus talking, the king's men arrived at the school with the palanquin. Yamunacharya worshipped the feet of his guru and calmly climbed into the palanquin, preparing himself for the great debate that was about to take place. A large crowd of people had gathered along the way, for it was unheard of that a 12 year old boy should challenge the court pandita and everyone wanted to catch a glimpse of the wonderful child. The brahmanas, many of whom had already been defeated by Kolahala, offered him blessings, saying "May you defeat this insolent pandita, just as Visnu in the form of a dwarf brahmana displaced Bali Maharaja, the king of the asuras".
Meanwhile, in the royal court a difference of opinion arose between the king and queen about Yamunacharya. The king said, "Just as a cat plays with a mouse, so will Kolahala defeat and destroy the boy."
But the queen was more thoughtful, realizing that Yamunacharya was no ordinary child. "Just as a small spark," she said, "can turn a mountain of cloth to ashes, so will this boy destroy the mountain-like pride of Kolahala."
"How can you really believe that this is possible?" exclaimed the king in amazement. "If you truly have faith in the child, then you must make a wager to back your words."
"Very well," replied the queen, "I will make a wager. If the boy does not defeat and humble the proud Kolahala, I will become the servant of your maidservant."
"This is certainly a mighty wager," said the king, "but I will match it. If the boy defeats Kolahala, as you say, then I will give him half of my kingdom."
While the king and queen were thus exchanging wagers, the palanquin arrived and Yamunacharya entered the palace. When Kolahala saw him, he looked at the queen and smiled sarcastically. "Alabandara," he said, meaning, "Is this the boy who will conquer me?"
"Yes" replied the queen quietly, "Ala-bandara. This is he who has come to conquer you."
The Contest
When the contestants were seated, Kolahala began the debate by putting simple questions on Sanskrit grammar to Yamunacharya. When, however, he found the boy could answer them with ease, he began to pose really difficult grammatical problems; but still, Yamunacharya replied to them all without difficulty.
He then spoke to the great pandita with a playful smile on his lips. "Because I am just a boy, you are insulting me by asking these simple questions. Remember that Astavakra was no older than myself when he defeated Bandi at the court of King Janaka. If you judge a person's learning by his size, then surely it follows that the water buffalo will be a greater scholar than yourself."
Although Kolahala winced at these words, he controlled his anger and replied smilingly, "Well answered. Now it is your turn to put questions to me."
"Very well" Yamunacharya responded, "I will put three propositions before you, and, if you can refute them, I shall accept defeat." Kolahala agreed and prepared to refute Yamunacharya's statements. "My first proposition is this" Yamunacharya spoke out clearly and boldly, "that your mother is not a barren woman. Refute this if you can."
Hearing this, Kolahala remained silent. "Had my mother been barren, my birth would not have been possible" he thought. "How can I refute this statement" Seeing Kolahala as silent as a dumb man, all the courtiers were astonished. Although the great pandita tried to conceal his anxiety, he could not prevent a flush from crossing his cheeks.
Yamunacharya spoke again, "Sir, if in spite of your all-conquering intelligence you are unable to refute my first proposition, then please hear my seond. It is this, that the Pandya king is supremely righteous. Refute this if you can." On hearing this Kolahala, was deeply disturbed, sensing his imminent defeat. With the king seated there in front of him, how could he deny the boy's statement? Again he remained silent, the color draining from his face as he was scarcely able to control his anger.
Yamunacharya spoke again, "Here is my third proposition – that the queen of the Pandya king is as chaste and faithful to her husband as was Savitri. Refute this if you can."
Seeing how he had once again been trapped by the intelligent boy, Kolahala could no longer restrain his anger. "You rascal" he screamed, "how can any loyal subject say that his king is unrighteous or his queen unfaithful to her husband? It is true I have not replied to your statements, but that does not mean I am defeated. First you must refute your own propositions, and, if you cannot, you should be put to death, for the implications of you words are treason against your king and queen."
When Kolahala shouted out these words, all his disciples and supporters cheered; but all those who favored Yamunacharya cried, "No, Kolahala is defeated. He is simply letting forth his anger, because he could not refute the statements of Yamunacharya as he promised to do".
Thus an argument broke out in the palace, but in the midst of the contention Yamunacharya quieted them all by saying, "Please stop this argument, for it is unnecessary. I shall refute all my propositions one by one. Please hear me." At this everyone fell silent and turned their attention to Yamunacharya, wondering how he could possibly do this and yet not offend the king and queen.
"My first statement" he continued,"was that our great pandita's mother was not a barren woman. However, it is stated in the Manu-samhita that a woman who has only one child is to be considered barren. As your mother gave birth to only one son, even though he is a man of such merit as yourself, according to the sastra, she must be considered barren. Secondly, I stated that the king of the Pandyas is a most righteous man. However, the Manu-samhita states that a king enjoys the benefit of one sixth of the religious acts of his subjects, but also has to bear the burden of one sixth of their sinful deeds. Because in the present age of Kali men are more prone toward sinfulness than piety, it must follow that our king, although flawless in his own character, is bearing a heavy burden of unrighteousness. And now to my third proposition, which stated that our queen is as chaste and faithful as was Savitri. But again, if we consult the laws of Manu, it is said that the king is the representative of Agni, Vayu, Surya, Chandra, Yama, Kuvera, Varuna, and Indra. Therefore, the queen is married not to just one man, but to these eight demigods as well. So how can it be said that she is chaste?"
On hearing these wonderful answers, all the people were filled with amazement, and the queen joyfully cried out, "Ala-bandara! Ala-bandara! He has conquered! He has conquered!"
The king immediately came forward and embraced Yamunacharya. "Just as on the rising of the sun" he said, "all the insignificant stars fade away, so you, O learned Alabandara, have conquered the proud Kolahala by your learning and skill. This fellow just a short while ago was demanding your death, now you may deal with him as you see fit. I have also promised to give you half my kingdom as a prize for this victory, and that promise I will certainly fulfill."
Of course, Yamunacharya forgave Kolahala, and, although he was but a boy of 12 years, he began at once to rule the kingdom he had won. Thus his days of poverty were over.

Source : http://gaudiyahistory.com/tag/yamunacharya/
--
Yours
Dinesh
Blog:http://dinesh-krsna.blogspot.com