He started politics at the Kantale Ceylon National Students' Union of the Communist Party at school age and was the President of the Communist Students' Union which he secretly started at Kantale Maha Vidyalaya. The Trincomalee District Branch of the Ceylon National Students' Union was established by Palitha Shamdas Solomons and Palitha Gurusinghe, student leaders from the Communist Party Headquarters. He started JVP politics in November 1968 while still in school through Angampodi Cyril Jayaratne, a teacher at Pulmudai Maha Vidyalaya. Piyasiri Gunaratne, a Trincomalee railway clerk born in Ambalangoda, conducted JVP classes for Gamanayake. Later he qualified for the Faculty of Arts at the
University of Colombo in 1969. Since 1976, he was the Unofficial Chief Secretary of JVP. With the banning of the JVP, Bopage's responsibilities were 'evaporated' and Gamanayake took over as the party's general secretary after 1984. When the JVP banned it in July 1983, Gamanayake was living in Part D of Bolamesawatta in Narahenpita. It is said that Gamanayake then retreated to Panagama in Ratnapura and stayed there for two weeks at the house of Major Gnanatilake Marasinghe. Later, he was active in the Eluwankulama area in the Puttalam district with party leaders including Wijeweera. Former Anuradhapura District Secretary Sisira Randeniya took care of Gamanayake after lifting the ban. When several JVP officials withdrew from their responsibilities, he reactivates JVP during ban after he was appointed as the new General Secretary. Later he was also known as Wilbert, Kalu Mahaththaya, Kuruppuge Gunasiri Dias and Dias Mudalali. Gamanayake and his family lived for some time in a village called Kajugaswatta near the Lenagala Rajamaha Viharaya on Ratnapura Road in Horana. They stayed in a house in the village for three years and continued to sew clothes as a home business. Meanwhile, he was caught by the police at work but was released one day as he was under a different name. After that incidence, he changed the residence. In his late years, Gamanayake was living in a house about 100 meters down the Model Lane, just south of the Mahawila Junction in Bandaragama, a few miles down Horana Road in Panadura under the name Kuruppuge Gunasiri Dias. He became popular as 'Dias Mudalali' as he ran a grocery store and a small sewing business in the house called "Nisansala". ==Assassination==